阵列元素的计数频率-yiteyi-C++库

给定一个可能包含副本的数组，打印所有元素及其频率。

null

例如：

Input :  arr[] = {10, 20, 20, 10, 10, 20, 5, 20}Output : 10 3         20 4         5  1Input : arr[] = {10, 20, 20}Output : 10 1         20 2

推荐：请尝试你的方法 {IDE} 首先，在进入解决方案之前。

A. 简单解决方案 就是运行两个循环。对于每项计数次数，它都会发生。为避免重复打印，请跟踪已处理的项目。

C++

                         // CPP program to count frequencies of array items                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         void                                     countFreq(                                     int                                     arr[],                                     int                                     n)                       
                         {                       
                                                 // Mark all array elements as not visited                       
                                                 vector<                                     bool                                     > visited(n,                                     false                                     );                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++) {                       
           
                                                 // Skip this element if already processed                       
                                                 if                                     (visited[i] ==                                     true                                     )                       
                                                 continue                                     ;                       
           
                                                 // Count frequency                       
                                                 int                                     count = 1;                       
                                                 for                                     (                                     int                                     j = i + 1; j < n; j++) {                       
                                                 if                                     (arr[i] == arr[j]) {                       
                                                 visited[j] =                                     true                                     ;                       
                                                 count++;                       
                                                 }                       
                                                 }                       
                                                 cout << arr[i] <<                                     " "                                     << count << endl;                       
                                                 }                       
                         }                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 20, 10, 10, 20, 5, 20 };                       
                                                 int                                     n =                                     sizeof                                     (arr) /                                     sizeof                                     (arr[0]);                       
                                                 countFreq(arr, n);                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // Java program to count frequencies of array items                       
                         import                                     java.util.Arrays;                       
           
                         class                                     GFG                       
                         {                       
                         public                                     static                                     void                                     countFreq(                                     int                                     arr[],                                     int                                     n)                       
                         {                       
                                                 boolean                                     visited[] =                                     new                                     boolean                                     [n];                       
                                   
                                                 Arrays.fill(visited,                                     false                                     );                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i =                                     0                                     ; i < n; i++) {                       
           
                                                 // Skip this element if already processed                       
                                                 if                                     (visited[i] ==                                     true                                     )                       
                                                 continue                                     ;                       
           
                                                 // Count frequency                       
                                                 int                                     count =                                     1                                     ;                       
                                                 for                                     (                                     int                                     j = i +                                     1                                     ; j < n; j++) {                       
                                                 if                                     (arr[i] == arr[j]) {                       
                                                 visited[j] =                                     true                                     ;                       
                                                 count++;                       
                                                 }                       
                                                 }                       
                                                 System.out.println(arr[i] +                                     " "                                     + count);                       
                                                 }                       
                         }                       
           
                         // Driver code                       
                         public                                     static                                     void                                     main(String []args)                       
                         {                       
                                                 int                                     arr[] =                                     new                                     int                                     []{                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     };                       
                                                 int                                     n = arr.length;                       
                                                 countFreq(arr, n);                       
                         }                       
                         }                       
           
                         // This code contributed by Adarsh_Verma.                       

Python3

                         # Python 3 program to count frequencies                       
                         # of array items                       
                         def                                     countFreq(arr, n):                       
                                   
                                                 # Mark all array elements as not visited                       
                                                 visited                                     =                                     [                                     False                                     for                                     i                                     in                                     range                                     (n)]                       
           
                                                 # Traverse through array elements                       
                                                 # and count frequencies                       
                                                 for                                     i                                     in                                     range                                     (n):                       
                                   
                                                 # Skip this element if already                       
                                                 # processed                       
                                                 if                                     (visited[i]                                     =                                     =                                     True                                     ):                       
                                                 continue                       
           
                                                 # Count frequency                       
                                                 count                                     =                                     1                       
                                                 for                                     j                                     in                                     range                                     (i                                     +                                     1                                     , n,                                     1                                     ):                       
                                                 if                                     (arr[i]                                     =                                     =                                     arr[j]):                       
                                                 visited[j]                                     =                                     True                       
                                                 count                                     +                                     =                                     1                       
                                   
                                                 print                                     (arr[i], count)                       
           
                         # Driver Code                       
                         if                                     __name__                                     =                                     =                                     '__main__'                                     :                       
                                                 arr                                     =                                     [                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     ]                       
                                                 n                                     =                                     len                                     (arr)                       
                                                 countFreq(arr, n)                       
                                   
                         # This code is contributed by                       
                         # Shashank_Sharma                       

C#

                         // C# program to count frequencies of array items                       
                         using                                     System;                       
           
                         class                                     GFG                       
                         {                       
                                                 public                                     static                                     void                                     countFreq(                                     int                                     []arr,                                     int                                     n)                       
                                                 {                       
                                                 bool                                     []visited =                                     new                                     bool                                     [n];                       
                                   
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 {                       
                                   
                                                 // Skip this element if already processed                       
                                                 if                                     (visited[i] ==                                     true                                     )                       
                                                 continue                                     ;                       
                                   
                                                 // Count frequency                       
                                                 int                                     count = 1;                       
                                                 for                                     (                                     int                                     j = i + 1; j < n; j++)                       
                                                 {                       
                                                 if                                     (arr[i] == arr[j])                       
                                                 {                       
                                                 visited[j] =                                     true                                     ;                       
                                                 count++;                       
                                                 }                       
                                                 }                       
                                                 Console.WriteLine(arr[i] +                                     " "                                     + count);                       
                                                 }                       
                                                 }                       
                                   
                                                 // Driver code                       
                                                 public                                     static                                     void                                     Main(String []args)                       
                                                 {                       
                                                 int                                     []arr =                                     new                                     int                                     []{ 10, 20, 20, 10, 10, 20, 5, 20 };                       
                                                 int                                     n = arr.Length;                       
                                                 countFreq(arr, n);                       
                                                 }                       
                         }                       
           
                         // This code has been contributed by 29AjayKumar                       

Javascript

                         <script>                       
           
                         // JavaScript program to count frequencies of array items                       
           
                         function                                     countFreq(arr, n)                       
                         {                       
                                                 let visited = Array.from({length: n}, (_, i) =>                                     false                                     );                       
                                   
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (let i = 0; i < n; i++) {                       
                                   
                                                 // Skip this element if already processed                       
                                                 if                                     (visited[i] ==                                     true                                     )                       
                                                 continue                                     ;                       
                                   
                                                 // Count frequency                       
                                                 let count = 1;                       
                                                 for                                     (let j = i + 1; j < n; j++) {                       
                                                 if                                     (arr[i] == arr[j]) {                       
                                                 visited[j] =                                     true                                     ;                       
                                                 count++;                       
                                                 }                       
                                                 }                       
                                                 document.write(arr[i] +                                     " "                                     + count +                                     "<br/>"                                     );                       
                                                 }                       
                         }                       
           
                         // Driver Code                       
           
                                                 let arr = [ 10, 20, 20, 10, 10, 20, 5, 20 ];                       
                                                 let n = arr.length;                       
                                                 countFreq(arr, n);                       
           
                         </script>                       

输出：

10 320 45 1

时间复杂性： O（n） ^2. ) 辅助空间： O（n）

一 有效解决方案 就是使用散列。

C++

                         // CPP program to count frequencies of array items                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         void                                     countFreq(                                     int                                     arr[],                                     int                                     n)                       
                         {                       
                                                 unordered_map<                                     int                                     ,                                     int                                     > mp;                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 mp[arr[i]]++;                       
           
                                                 // Traverse through map and print frequencies                       
                                                 for                                     (                                     auto                                     x : mp)                       
                                                 cout << x.first <<                                     " "                                     << x.second << endl;                       
                         }                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 20, 10, 10, 20, 5, 20 };                       
                                                 int                                     n =                                     sizeof                                     (arr) /                                     sizeof                                     (arr[0]);                       
                                                 countFreq(arr, n);                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // Java program to count frequencies of array items                       
                         import                                     java.util.*;                       
           
                         class                                     GFG                       
                         {                       
           
                                                 static                                     void                                     countFreq(                                     int                                     arr[],                                     int                                     n)                       
                                                 {                       
                                                 Map<Integer, Integer> mp =                                     new                                     HashMap<>();                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i =                                     0                                     ; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.containsKey(arr[i]))                       
                                                 {                       
                                                 mp.put(arr[i], mp.get(arr[i]) +                                     1                                     );                       
                                                 }                       
                                                 else                       
                                                 {                       
                                                 mp.put(arr[i],                                     1                                     );                       
                                                 }                       
                                                 }                       
                                                 // Traverse through map and print frequencies                       
                                                 for                                     (Map.Entry<Integer, Integer> entry : mp.entrySet())                       
                                                 {                       
                                                 System.out.println(entry.getKey() +                                     " "                                     + entry.getValue());                       
                                                 }                       
                                                 }                       
           
                                                 // Driver code                       
                                                 public                                     static                                     void                                     main(String args[])                       
                                                 {                       
                                                 int                                     arr[] = {                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     };                       
                                                 int                                     n = arr.length;                       
                                                 countFreq(arr, n);                       
                                                 }                       
                         }                       
           
                         // This code contributed by Rajput-Ji                       

Python3

                         # Python3 program to count frequencies                       
                         # of array items                       
                         def                                     countFreq(arr, n):                       
           
                                                 mp                                     =                                     dict                                     ()                       
           
                                                 # Traverse through array elements                       
                                                 # and count frequencies                       
                                                 for                                     i                                     in                                     range                                     (n):                       
                                                 if                                     arr[i]                                     in                                     mp.keys():                       
                                                 mp[arr[i]]                                     +                                     =                                     1                       
                                                 else                                     :                       
                                                 mp[arr[i]]                                     =                                     1                       
                                   
                                                 # Traverse through map and print                       
                                                 # frequencies                       
                                                 for                                     x                                     in                                     mp:                       
                                                 print                                     (x,                                     " "                                     , mp[x])                       
           
                         # Driver code                       
                         arr                                     =                                     [                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     ]                       
                         n                                     =                                     len                                     (arr)                       
                         countFreq(arr, n)                       
           
                         # This code is contributed by                       
                         # Mohit kumar 29                       

C#

                         // C# implementation of the approach                       
                         using                                     System;                       
                         using                                     System.Collections.Generic;                       
           
                         class                                     GFG                       
                         {                       
           
                                                 static                                     void                                     countFreq(                                     int                                     []arr,                                     int                                     n)                       
                                                 {                       
                                                 Dictionary<                                     int                                     ,                                     int                                     > mp =                                     new                                     Dictionary<                                     int                                     ,                                     int                                     >();                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.ContainsKey(arr[i]))                       
                                                 {                       
                                                 var                                     val = mp[arr[i]];                       
                                                 mp.Remove(arr[i]);                       
                                                 mp.Add(arr[i], val + 1);                       
                                                 }                       
                                                 else                       
                                                 {                       
                                                 mp.Add(arr[i], 1);                       
                                                 }                       
                                                 }                       
                                   
                                                 // Traverse through map and print frequencies                       
                                                 foreach                                     (KeyValuePair<                                     int                                     ,                                     int                                     > entry                                     in                                     mp)                       
                                                 {                       
                                                 Console.WriteLine(entry.Key +                                     " "                                     + entry.Value);                       
                                                 }                       
                                                 }                       
           
                                                 // Driver code                       
                                                 public                                     static                                     void                                     Main(String []args)                       
                                                 {                       
                                                 int                                     []arr = {10, 20, 20, 10, 10, 20, 5, 20};                       
                                                 int                                     n = arr.Length;                       
                                                 countFreq(arr, n);                       
                                                 }                       
                         }                       
           
                         /* This code contributed by PrinciRaj1992 */                       

Javascript

                         <script>                       
           
           
                         // JavaScript program to count                       
                         // frequencies of array items                       
           
                         function                                     countFreq(arr, n)                       
                         {                       
                                                 var                                     mp =                                     new                                     Map();                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     var                                     i = 0; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.has(arr[i]))                       
                                                 mp.set(arr[i], mp.get(arr[i])+1)                       
                                                 else                       
                                                 mp.set(arr[i], 1)                       
                                                 }                       
           
                                                 var                                     keys = [];                       
                                                 mp.forEach((value, key) => {                       
                                                 keys.push(key);                       
                                                 });                       
                                                 keys.sort((a,b)=> a-b);                       
                                   
                                                 // Traverse through map and print frequencies                       
                                                 keys.forEach((key) => {                       
                                   
                                                 document.write(key +                                     " "                                     + mp.get(key)+                                     "<br>"                                     );                       
                                                 });                       
                         }                       
           
                         var                                     arr = [10, 20, 20, 10, 10, 20, 5, 20];                       
                         var                                     n = arr.length;                       
                         countFreq(arr, n);                       
           
                         </script>                       

输出：

5 110 320 4

时间复杂性： O（n） 辅助空间： O（n）

在上述高效的解决方案中，如何按元素在输入中的显示顺序打印元素？

C++

                         // CPP program to count frequencies of array items                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         void                                     countFreq(                                     int                                     arr[],                                     int                                     n)                       
                         {                       
                                                 unordered_map<                                     int                                     ,                                     int                                     > mp;                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 mp[arr[i]]++;                       
           
                                                 // To print elements according to first                       
                                                 // occurrence, traverse array one more time                       
                                                 // print frequencies of elements and mark                       
                                                 // frequencies as -1 so that same element                       
                                                 // is not printed multiple times.                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++) {                       
                                                 if                                     (mp[arr[i]] != -1)                       
                                                 {                       
                                                 cout << arr[i] <<                                     " "                                     << mp[arr[i]] << endl;                       
                                                 mp[arr[i]] = -1;                       
                                                 }                       
                                                 }                       
                         }                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = { 10, 20, 20, 10, 10, 20, 5, 20 };                       
                                                 int                                     n =                                     sizeof                                     (arr) /                                     sizeof                                     (arr[0]);                       
                                                 countFreq(arr, n);                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // Java program to count frequencies of array items                       
                         import                                     java.util.*;                       
           
                         class                                     GFG                       
                         {                       
           
                                                 static                                     void                                     countFreq(                                     int                                     arr[],                                     int                                     n)                       
                                                 {                       
                                                 Map<Integer, Integer> mp =                                     new                                     HashMap<>();                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     int                                     i =                                     0                                     ; i < n; i++)                       
                                                 {                       
                                                 mp.put(arr[i], mp.get(arr[i]) ==                                     null                                     ?                                     1                                     : mp.get(arr[i]) +                                     1                                     );                       
                                                 }                       
           
                                                 // To print elements according to first                       
                                                 // occurrence, traverse array one more time                       
                                                 // print frequencies of elements and mark                       
                                                 // frequencies as -1 so that same element                       
                                                 // is not printed multiple times.                       
                                                 for                                     (                                     int                                     i =                                     0                                     ; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.get(arr[i]) != -                                     1                                     )                       
                                                 {                       
                                                 System.out.println(arr[i] +                                     " "                                     + mp.get(arr[i]));                       
                                                 mp.put(arr[i], -                                     1                                     );                       
                                                 }                       
                                                 }                       
                                                 }                       
           
                                                 // Driver code                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 int                                     arr[] = {                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     };                       
                                                 int                                     n = arr.length;                       
                                                 countFreq(arr, n);                       
                                                 }                       
                         }                       
           
                         // This code contributed by Rajput-Ji                       

Python3

                         # Python3 program to count frequencies of array items                       
                         def                                     countFreq(arr, n):                       
                                   
                                                 mp                                     =                                     {}                       
                                   
                                                 # Traverse through array elements and                       
                                                 # count frequencies                       
                                                 for                                     i                                     in                                     range                                     (n):                       
                                                 if                                     arr[i]                                     not                                     in                                     mp:                       
                                                 mp[arr[i]]                                     =                                     0                       
                                                 mp[arr[i]]                                     +                                     =                                     1                       
                                   
                                                 # To print elements according to first                       
                                                 # occurrence, traverse array one more time                       
                                                 # print frequencies of elements and mark                       
                                                 # frequencies as -1 so that same element                       
                                                 # is not printed multiple times.                       
                                                 for                                     i                                     in                                     range                                     (n):                       
                                                 if                                     (mp[arr[i]] !                                     =                                     -                                     1                                     ):                       
                                                 print                                     (arr[i],mp[arr[i]])                       
                                                 mp[arr[i]]                                     =                                     -                                     1                       
           
                         # Driver code                       
           
                         arr                                     =                                     [                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     ]                       
                         n                                     =                                     len                                     (arr)                       
                         countFreq(arr, n)                       
           
                         # This code is contributed by shubhamsingh10                       

C#

                         // C# program to count frequencies of array items                       
                         using                                     System;                       
                         using                                     System.Collections.Generic;                       
           
                         class                                     GFG                       
                         {                       
           
                                                 static                                     void                                     countFreq(                                     int                                     []arr,                                     int                                     n)                       
                                                 {                       
                                                 Dictionary<                                     int                                     ,                                     int                                     > mp =                                     new                                     Dictionary<                                     int                                     ,                                     int                                     >();                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                   
                                                 for                                     (                                     int                                     i = 0 ; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.ContainsKey(arr[i]))                       
                                                 {                       
                                                 var                                     val = mp[arr[i]];                       
                                                 mp.Remove(arr[i]);                       
                                                 mp.Add(arr[i], val + 1);                       
                                                 }                       
                                                 else                       
                                                 {                       
                                                 mp.Add(arr[i], 1);                       
                                                 }                       
                                                 }                       
           
                                                 // To print elements according to first                       
                                                 // occurrence, traverse array one more time                       
                                                 // print frequencies of elements and mark                       
                                                 // frequencies as -1 so that same element                       
                                                 // is not printed multiple times.                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.ContainsKey(arr[i]) && mp[arr[i]] != -1)                       
                                                 {                       
                                                 Console.WriteLine(arr[i] +                                     " "                                     + mp[arr[i]]);                       
                                                 mp.Remove(arr[i]);                       
                                                 mp.Add(arr[i], -1);                       
                                                 }                       
                                                 }                       
                                                 }                       
           
                                                 // Driver code                       
                                                 public                                     static                                     void                                     Main(String[] args)                       
                                                 {                       
                                                 int                                     []arr = {10, 20, 20, 10, 10, 20, 5, 20};                       
                                                 int                                     n = arr.Length;                       
                                                 countFreq(arr, n);                       
                                                 }                       
                         }                       
           
                         // This code is contributed by Princi Singh                       

Javascript

                         <script>                       
           
           
                         // Javascript program to count frequencies of array items                       
           
                         function                                     countFreq(arr, n)                       
                         {                       
                                                 var                                     mp =                                     new                                     Map();                       
           
                                                 // Traverse through array elements and                       
                                                 // count frequencies                       
                                                 for                                     (                                     var                                     i = 0; i < n; i++)                       
                                                 {                       
                                                 if                                     (mp.has(arr[i]))                       
                                                 mp.set(arr[i], mp.get(arr[i])+1)                       
                                                 else                       
                                                 mp.set(arr[i], 1)                       
                                                 }                       
                                   
                                                 // To print elements according to first                       
                                                 // occurrence, traverse array one more time                       
                                                 // print frequencies of elements and mark                       
                                                 // frequencies as -1 so that same element                       
                                                 // is not printed multiple times.                       
                                                 for                                     (                                     var                                     i = 0; i < n; i++) {                       
                                                 if                                     (mp.get(arr[i]) != -1)                       
                                                 {                       
                                                 document.write( arr[i] +                                     " "                                     + mp.get(arr[i]) +                                     "<br>"                                     );                       
                                                 mp.set(arr[i], -1);                       
                                                 }                       
                                                 }                       
                         }                       
           
                         var                                     arr = [10, 20, 20, 10, 10, 20, 5, 20];                       
                         var                                     n = arr.length;                       
                         countFreq(arr, n);                       
           
                         // This code is contributed by rrrtnx.                       
                         </script>                       

输出：

10 320 45 1

时间复杂性： O（n） 辅助空间： O（n）

这个问题可以通过使用Hashmap在Java中解决。以下是节目。

C++

                         // C++ program to count frequencies of                       
                         // integers in array using Hashmap                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         void                                     frequencyNumber(                                     int                                     arr[],                                     int                                     size)                       
                         {                       
                                   
                                                 // Creating a HashMap containing integer                       
                                                 // as a key and occurrences as a value                       
                                                 unordered_map<                                     int                                     ,                                     int                                     >freqMap;                       
           
                                                 for                                     (                                     int                                     i=0;i<size;i++) {                       
                                                 freqMap[arr[i]]++;                       
                                                 }                       
           
                                                 // Printing the freqMap                       
                                                 for                                     (                                     auto                                     it : freqMap) {                       
                                                 cout<<it.first<<                                     " "                                     <<it.second<<endl;                       
                                                 }                       
                         }                       
           
                         int                                     main()                       
                         {                       
                                                 int                                     arr[] = {10, 20, 20, 10, 10, 20, 5, 20};                       
                                                 int                                     size =                                     sizeof                                     (arr)/                                     sizeof                                     (arr[0]);                       
                                                 frequencyNumber(arr,size);                       
                         }                       
           
                         // This code is contributed by shinjanpatra.                       

JAVA

                         // Java program to count frequencies of                       
                         // integers in array using Hashmap                       
                         import                                     java.io.*;                       
                         import                                     java.util.*;                       
                         class                                     OccurenceOfNumberInArray {                       
                                                 static                                     void                                     frequencyNumber(                                     int                                     arr[],                                     int                                     size)                       
                                                 {                       
                                                 // Creating a HashMap containing integer                       
                                                 // as a key and occurrences as a value                       
                                                 HashMap<Integer, Integer> freqMap                       
                                                 =                                     new                                     HashMap<Integer, Integer>();                       
           
                                                 for                                     (                                     int                                     i=                                     0                                     ;i<size;i++) {                       
                                                 if                                     (freqMap.containsKey(arr[i])) {                       
           
                                                 // If number is present in freqMap,                       
                                                 // incrementing it's count by 1                       
                                                 freqMap.put(arr[i], freqMap.get(arr[i]) +                                     1                                     );                       
                                                 }                       
                                                 else                                     {                       
           
                                                 // If integer is not present in freqMap,                       
                                                 // putting this integer to freqMap with 1 as it's value                       
                                                 freqMap.put(arr[i],                                     1                                     );                       
                                                 }                       
                                                 }                       
           
                                                 // Printing the freqMap                       
                                                 for                                     (Map.Entry entry : freqMap.entrySet()) {                       
                                                 System.out.println(entry.getKey() +                                     " "                                     + entry.getValue());                       
                                                 }                       
                                                 }                       
           
                                                 // Driver Code                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 int                                     arr[] = {                                     10                                     ,                                     20                                     ,                                     20                                     ,                                     10                                     ,                                     10                                     ,                                     20                                     ,                                     5                                     ,                                     20                                     };                       
                                                 int                                     size = arr.length;                       
                                                 frequencyNumber(arr,size);                       
                                                 }                       
                         }                       

Javascript

                         <script>                       
                         // Javascript program to count frequencies of                       
                         // integers in array using Hashmap                       
           
                         function                                     frequencyNumber(arr,size)                       
                         {                       
                                                 // Creating a HashMap containing integer                       
                                                 // as a key and occurrences as a value                       
                                                 let freqMap                       
                                                 =                                     new                                     Map();                       
                                   
                                                 for                                     (let i=0;i<size;i++) {                       
                                                 if                                     (freqMap.has(arr[i])) {                       
                                   
                                                 // If number is present in freqMap,                       
                                                 // incrementing it's count by 1                       
                                                 freqMap.set(arr[i], freqMap.get(arr[i]) + 1);                       
                                                 }                       
                                                 else                                     {                       
                                   
                                                 // If integer is not present in freqMap,                       
                                                 // putting this integer to freqMap with 1 as it's value                       
                                                 freqMap.set(arr[i], 1);                       
                                                 }                       
                                                 }                       
                                   
                                                 // Printing the freqMap                       
                                                 for                                     (let [key, value] of freqMap.entries()) {                       
                                                 document.write(key +                                     " "                                     + value+                                     "<br>"                                     );                       
                                                 }                       
                         }                       
           
                         // Driver Code                       
                         let arr=[10, 20, 20, 10, 10, 20, 5, 20];                       
                         let size = arr.length;                       
                         frequencyNumber(arr,size);                       
           
                         // This code is contributed by patel2127                       
                         </script>                       

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