打印给定字符串中素索引处的字符的程序-yiteyi-C++库

给定一个字符串，我们的任务是打印素数索引中的字符。

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例如：

Input : I love programming Output : lv ganExplanation :prime index characters in a string are : lv gan          Input : Happy coding everyoneOutput : apycn ro

图片[1]-打印给定字符串中素索引处的字符的程序-yiteyi-C++库

推荐：请尝试你的方法 {IDE} 首先，在进入解决方案之前。

方法：

使用两个循环将数字除以字符串的长度。
余数为0时递增变量结果。
如果变量result=1，则打印相应的字符。

以下是上述方法的实施情况：

C++

                         // C++ Program to print Characters at                       
                         // Prime index in a given String                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         bool                                     isPrime(                                     int                                     n)                       
                         {                       
                                                 // Corner case                       
                                                 if                                     (n <= 1)                                     return                                     false                                     ;                       
           
                                                 // Check from 2 to n-1                       
                                                 for                                     (                                     int                                     i = 2; i < n; i++)                       
                                                 if                                     (n % i == 0)                       
                                                 return                                     false                                     ;                       
           
                                                 return                                     true                                     ;                       
                         }                       
           
                         // Function to print                       
                         // character at prime index                       
                         void                                     prime_index(string input)                       
                         {                       
                                                 int                                     n = input.length();                       
           
                                                 // Loop to check if                       
                                                 // index prime or not                       
                                                 for                                     (                                     int                                     i = 2; i <= n; i++)                       
                                                 if                                     (isPrime(i))                       
                                                 cout << input[i - 1];                       
                         }                       
           
                         // Driver Code                       
                         int                                     main()                       
                         {                       
                                                 string input =                                     "GeeksforGeeks"                                     ;                       
                                                 prime_index(input);                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // Java Program to print                       
                         // Characters at Prime index                       
                         // in a given String                       
                         class                                     GFG                       
                         {                       
                                                 static                                     boolean                                     isPrime(                                     int                                     n)                       
                                                 {                       
                                                 // Corner case                       
                                                 if                                     (n <=                                     1                                     )                                     return                                     false                                     ;                       
                                   
                                                 // Check from 2 to n-1                       
                                                 for                                     (                                     int                                     i =                                     2                                     ; i < n; i++)                       
                                                 if                                     (n % i ==                                     0                                     )                       
                                                 return                                     false                                     ;                       
                                   
                                                 return                                     true                                     ;                       
                                                 }                       
                                   
                                                 // Function to print                       
                                                 // character at prime index                       
                                                 static                                     void                                     prime_index(String input)                       
                                                 {                       
                                                 int                                     n = input.length();                       
                                   
                                                 // Loop to check if                       
                                                 // index prime or not                       
                                                 for                                     (                                     int                                     i =                                     2                                     ; i <= n; i++)                       
                                                 if                                     (isPrime(i))                       
           
                                                 System.out.print                       
                                                 (input.charAt(i -                                     1                                     ));                       
                                                 }                       
                                   
                                                 // Driver code                       
                                                 public                                     static                                     void                                     main (String[] args)                       
                                                 {                       
                                                 String input =                                     "GeeksforGeeks"                                     ;                       
                                   
                                                 prime_index(input);                       
                                                 }                       
                         }                       
           
                         // This code is contributed by Anant Agarwal.                       

Python3

                         # Python3 program to print                       
                         # Characters at Prime index                       
                         # in a given String                       
           
                         def                                     isPrime(n):                       
           
                                                 # Corner case                       
                                                 if                                     n <                                     =                                     1                                     :                       
                                                 return                                     False                       
           
                                                 # Check from 2 to n-1                       
                                                 for                                     i                                     in                                     range                                     (                                     2                                     , n):                       
                                                 if                                     n                                     %                                     i                                     =                                     =                                     0                                     :                       
                                                 return                                     False                                     ;                       
           
                                                 return                                     True                       
           
                         # Function to print                       
                         # character at prime index                       
                         def                                     prime_index (                                     input                                     ):                       
                                                 p                                     =                                     list                                     (                                     input                                     )                       
                                                 s                                     =                                     ""                       
                                   
                                                 # Loop to check if                       
                                                 # index prime or not                       
                                                 for                                     i                                     in                                     range                                     (                                     2                                     ,                                     len                                     (p)                                     +                                     1                                     ):                       
                                                 if                                     isPrime(i):                       
                                                 s                                     =                                     s                                     +                                     input                                     [i                                     -                                     1                                     ]                       
                                                 print                                     (s)                       
                                   
                         # Driver Code                       
                         input                                     =                                     "GeeksforGeeks"                       
                         prime_index(                                     input                                     )                       

C#

                         // C# Program to print Characters                       
                         // at Prime index in a given String                       
                         using                                     System;                       
           
                         class                                     GFG                       
                         {                       
                                                 static                                     bool                                     isPrime(                                     int                                     n)                       
                                                 {                       
                                                 // Corner case                       
                                                 if                                     (n <= 1)                                     return                                     false                                     ;                       
                                   
                                                 // Check from 2 to n-1                       
                                                 for                                     (                                     int                                     i = 2; i < n; i++)                       
                                                 if                                     (n % i == 0)                       
                                                 return                                     false                                     ;                       
                                   
                                                 return                                     true                                     ;                       
                                                 }                       
                                   
                                                 // Function to print character                       
                                                 // at prime index                       
                                                 static                                     void                                     prime_index(                                     string                                     input)                       
                                                 {                       
                                                 int                                     n = input.Length;                       
                                   
                                                 // Loop to check if                       
                                                 // index prime or not                       
                                                 for                                     (                                     int                                     i = 2; i <= n; i++)                       
                                                 if                                     (isPrime(i))                       
           
                                   
                                                 Console.Write(input[i - 1]);                       
                                                 }                       
                                   
                                                 // Driver code                       
                                                 public                                     static                                     void                                     Main ()                       
                                                 {                       
                                                 string                                     input =                                     "GeeksforGeeks"                                     ;                       
                                   
                                                 prime_index(input);                       
                                                 }                       
                         }                       
           
                         // This code is contributed by Vt_m.                       

PHP

                         <?php                       
                         // PHP Program to print                       
                         // Characters at Prime                       
                         // index in a given String                       
           
                         function                                     isPrime(                                     $n                                     )                       
                         {                       
                                                 // Corner case                       
                                                 if                                     (                                     $n                                     <= 1)                                     return                                     false;                       
           
                                                 // Check from 2 to n-1                       
                                                 for                                     (                                     $i                                     = 2;                                     $i                                     <                                     $n                                     ;                                     $i                                     ++)                       
                                                 if                                     (                                     $n                                     %                                     $i                                     == 0)                       
                                                 return                                     false;                       
           
                                                 return                                     true;                       
                         }                       
           
                         // Function to print                       
                         // character at prime index                       
                         function                                     prime_index(                                     $input                                     )                       
                         {                       
                                                 $n                                     =                                     strlen                                     (                                     $input                                     );                       
           
                                                 // Loop to check if                       
                                                 // index prime or not                       
                                                 for                                     (                                     $i                                     = 2;                                     $i                                     <=                                     $n                                     ;                                     $i                                     ++)                       
                                                 if                                     (isPrime(                                     $i                                     ))                       
                                                 echo                                     $input                                     [                                     $i                                     - 1];                       
                         }                       
           
                         // Driver Code                       
                         $input                                     =                                     "GeeksforGeeks"                                     ;                       
                         prime_index(                                     $input                                     );                       
           
                         // This code is contributed by ajit.                       
                         ?>                       

Javascript

                         <script>                       
           
                         // Javascript program to print characters                       
                         // at Prime index in a given String                       
                         function                                     isPrime(n)                       
                         {                       
                                   
                                                 // Corner case                       
                                                 if                                     (n <= 1)                                     return                                     false                                     ;                       
                                   
                                                 // Check from 2 to n-1                       
                                                 for                                     (let i = 2; i < n; i++)                       
                                                 if                                     (n % i == 0)                       
                                                 return                                     false                                     ;                       
                                   
                                                 return                                     true                                     ;                       
                         }                       
                                   
                         // Function to print character                       
                         // at prime index                       
                         function                                     prime_index(input)                       
                         {                       
                                                 let n = input.length;                       
                                   
                                                 // Loop to check if                       
                                                 // index prime or not                       
                                                 for                                     (let i = 2; i <= n; i++)                       
                                                 if                                     (isPrime(i))                       
                                                 document.write(input[i - 1]);                       
                         }                       
           
                         // Driver code                       
                         let input =                                     "GeeksforGeeks"                                     ;                       
                                   
                         prime_index(input);                       
           
                         // This code is contributed by suresh07                       
           
                         </script>                       

输出：

eesoes

优化： 对于大字符串，我们可以使用埃拉托斯坦筛有效地找到所有小于或等于字符串长度的素数。

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