计算整数位数的程序（4种不同的方法）-yiteyi-C++库

计算用户输入的长整数的位数。

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图片[1]-计算整数位数的程序（4种不同的方法）-yiteyi-C++库

简单迭代解 用户输入的整数存储在变量n中。然后while循环被迭代，直到测试表达式n！=0被计算为0（false）。

在第一次迭代之后，n的值将是345，计数将增加到1。
第二次迭代后，n的值将为34，计数将增加到2。
在第三次迭代之后，n的值将是3，计数将增加到3。
在第四次迭代开始时，n的值将为0，循环终止。

然后对测试表达式求值为false，循环终止。

C++

                         // Iterative C++ program to count                       
                         // number of digits in a number                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         int                                     countDigit(                                     long                                     long                                     n)                       
                         {                       
                                                 int                                     count = 0;                       
                                                 while                                     (n != 0)                       
                                                 {                       
                                                 n = n / 10;                       
                                                 ++count;                       
                                                 }                       
                                                 return                                     count;                       
                         }                       
           
                         // Driver code                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 long                                     long                                     n = 345289467;                       
                                                 cout <<                                     "Number of digits : "                                     << countDigit(n);                       
                                                 return                                     0;                       
                         }                       
           
                         // This code is contributed                       
                         // by Akanksha Rai                       

C

                         // Iterative C program to count number of                       
                         // digits in a number                       
                         #include <stdio.h>                       
           
                         int                                     countDigit(                                     long                                     long                                     n)                       
                         {                       
                                                 int                                     count = 0;                       
                                                 while                                     (n != 0)                       
                                                 {                       
                                                 n = n / 10;                       
                                                 ++count;                       
                                                 }                       
                                                 return                                     count;                       
                         }                       
           
                         // Driver code                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 long                                     long                                     n = 345289467;                       
                                                 printf                                     (                                     "Number of digits : %d"                                     , countDigit(n));                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // JAVA Code to count number of                       
                         // digits in an integer                       
                         class                                     GFG {                       
           
                                                 static                                     int                                     countDigit(                                     long                                     n)                       
                                                 {                       
                                                 int                                     count =                                     0                                     ;                       
                                                 while                                     (n !=                                     0                                     ) {                       
                                                 n = n /                                     10                                     ;                       
                                                 ++count;                       
                                                 }                       
                                                 return                                     count;                       
                                                 }                       
           
                                                 /* Driver code */                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 long                                     n =                                     345289467                                     ;                       
                                                 System.out.print(                                     "Number of digits : "                       
                                                 + countDigit(n));                       
                                                 }                       
                         }                       
                         // This code is contributed by Arnav Kr. Mandal.                       

Python3

                         # Iterative Python program to count                       
                         # number of digits in a number                       
           
           
                         def                                     countDigit(n):                       
                                                 count                                     =                                     0                       
                                                 while                                     n !                                     =                                     0                                     :                       
                                                 n                                     /                                     /                                     =                                     10                       
                                                 count                                     +                                     =                                     1                       
                                                 return                                     count                       
           
           
                         # Driver Code                       
                         n                                     =                                     345289467                       
                         print                                     (                                     "Number of digits : % d"                                     %                                     (countDigit(n)))                       
           
                         # This code is contributed by Shreyanshi Arun                       

C#

                         // C# Code to count number of                       
                         // digits in an integer                       
                         using                                     System;                       
           
                         class                                     GFG {                       
           
                                                 static                                     int                                     countDigit(                                     long                                     n)                       
                                                 {                       
                                                 int                                     count = 0;                       
                                                 while                                     (n != 0)                       
                                                 {                       
                                                 n = n / 10;                       
                                                 ++count;                       
                                                 }                       
                                                 return                                     count;                       
                                                 }                       
           
                                                 /* Driver code */                       
                                                 public                                     static                                     void                                     Main()                       
                                                 {                       
                                                 long                                     n = 345289467;                       
                                                 Console.WriteLine(                                     "Number of"                       
                                                 +                                     " digits : "                                     + countDigit(n));                       
                                                 }                       
                         }                       
           
                         // This code is contributed by anuj_67.                       

PHP

                         <?php                       
                         // Iterative PHP program to count                       
                         // number of digits in a number                       
           
                         function                                     countDigit(                                     $n                                     )                       
                         {                       
                                                 $count                                     = 0;                       
                                                 while                                     (                                     $n                                     != 0)                       
                                                 {                       
                                                 $n                                     =                                     round                                     (                                     $n                                     / 10);                       
                                                 ++                                     $count                                     ;                       
                                                 }                       
                                                 return                                     $count                                     ;                       
                         }                       
           
                         // Driver code                       
                         $n                                     = 345289467;                       
                         echo                                     "Number of digits : "                       
                                                 . countDigit(                                     $n                                     );                       
           
                         //This code is contributed by mits                       
                         ?>                       

Javascript

                         <script>                       
           
                         // Iterative Javascript program to count                       
                         // number of digits in a number                       
           
                         function                                     countDigit(n)                       
                         {                       
                                                 let count = 0;                       
                                                 while                                     (n != 0)                       
                                                 {                       
                                                 n = Math.floor(n / 10);                       
                                                 ++count;                       
                                                 }                       
                                                 return                                     count;                       
                         }                       
           
                         // Driver code                       
           
                                                 n = 345289467;                       
                                                 document.write(                                     "Number of digits : "                                     + countDigit(n));                       
                                   
                         // This code is contributed by Mayank Tyagi                       
           
                         </script>                       

输出

Number of digits : 9

递归解决方案：

C++

                         // Recursive C++ program to count number of                       
                         // digits in a number                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         int                                     countDigit(                                     long                                     long                                     n)                       
                         {                       
                                                 if                                     (n/10 == 0)                       
                                                 return                                     1;                       
                                                 return                                     1 + countDigit(n / 10);                       
                         }                       
           
                         // Driver code                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 long                                     long                                     n = 345289467;                       
                                                 cout <<                                     "Number of digits :"                                     << countDigit(n);                       
                                                 return                                     0;                       
                         }                       
                         // This code is contributed by Mukul Singh.                       

C

                         // Recursive C program to count number of                       
                         // digits in a number                       
                         #include <stdio.h>                       
           
                         int                                     countDigit(                                     long                                     long                                     n)                       
                         {                       
                                                 if                                     (n/10 == 0)                       
                                                 return                                     1;                       
                                                 return                                     1 + countDigit(n / 10);                       
                         }                       
           
                         // Driver code                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 long                                     long                                     n = 345289467;                       
                                                 printf                                     (                                     "Number of digits : %d"                                     , countDigit(n));                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // JAVA Code to count number of                       
                         // digits in an integer                       
                         import                                     java.util.*;                       
           
                         class                                     GFG {                       
           
                                                 static                                     int                                     countDigit(                                     long                                     n)                       
                                                 {                       
                                                 if                                     (n/                                     10                                     ==                                     0                                     )                       
                                                 return                                     1                                     ;                       
                                                 return                                     1                                     + countDigit(n /                                     10                                     );                       
                                                 }                       
           
                                                 /* Driver code */                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 long                                     n =                                     345289467                                     ;                       
                                                 System.out.print(                                     "Number of digits : "                       
                                                 + countDigit(n));                       
                                                 }                       
                         }                       
           
                         // This code is contributed by Arnav Kr. Mandal.                       

Python3

                         # Recursive Python program to count                       
                         # number of digits in a number                       
           
           
                         def                                     countDigit(n):                       
                                                 if                                     n                                     /                                     10                                     =                                     =                                     0                                     :                       
                                                 return                                     1                       
                                                 return                                     1                                     +                                     countDigit(n                                     /                                     /                                     10                                     )                       
           
           
                         # Driver Code                       
                         n                                     =                                     345289467                       
                         print                                     (                                     "Number of digits : % d"                                     %                                     (countDigit(n)))                       
           
                         # This code is contributed by Shreyanshi Arun                       

C#

                         // C# Code to count number of                       
                         // digits in an integer                       
                         using                                     System;                       
           
                         class                                     GFG {                       
           
                                                 static                                     int                                     countDigit(                                     long                                     n)                       
                                                 {                       
                                                 if                                     (n/10 == 0)                       
                                                 return                                     1;                       
                                                 return                                     1 + countDigit(n / 10);                       
                                                 }                       
           
                                                 /* Driver Code */                       
                                                 public                                     static                                     void                                     Main()                       
                                                 {                       
                                                 long                                     n = 345289467;                       
                                                 Console.WriteLine(                                     "Number of "                       
                                                 +                                     "digits : "                       
                                                 + countDigit(n));                       
                                                 }                       
                         }                       
           
                         // This code is contributed by anuj_67.                       

PHP

                         <?php                       
                         // Recursive PHP program to count                       
                         // number of digits in a number                       
           
                         function                                     countDigit(                                     $n                                     )                       
                         {                       
                                                 if                                     (                                     $n                                     /10 == 0)                       
                                                 return                                     1;                       
                                                 return                                     1 + countDigit((int)(                                     $n                                     / 10));                       
                         }                       
           
                         // Driver Code                       
                         $n                                     = 345289467;                       
                         print                                     (                                     "Number of digits : "                                     .                       
                                                 (countDigit(                                     $n                                     )));                       
           
                         // This code is contributed by mits                       
                         ?>                       

Javascript

                         <script>                       
           
                         // Recursive Javascript program to count number of                       
                         // digits in a number                       
           
                         function                                     countDigit(n)                       
                         {                       
                                                 if                                     (n/10 == 0)                       
                                                 return                                     1;                       
                                                 return                                     1 + countDigit(parseInt(n / 10));                       
                         }                       
           
                         // Driver code                       
                         var                                     n = 345289467;                       
                         document.write(                                     "Number of digits :"                                     + countDigit(n));                       
           
                         </script>                       

输出

Number of digits :9

基于日志的解决方案： 我们可以使用log10（以10为底的对数）来计算正数的位数（负数不定义对数）。数字计数 N=log10（N）的上限 .

C++

                         // Log based C++ program to count number of                       
                         // digits in a number                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         int                                     countDigit(                                     long                                     long                                     n) {                       
                                                 return                                     floor                                     (                                     log10                                     (n) + 1);                       
                         }                       
           
                         // Driver code                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 long                                     long                                     n = 345289467;                       
                                                 cout <<                                     "Number of digits : "                       
                                                 << countDigit(n);                       
                                                 return                                     0;                       
                         }                       
           
                         // This code is contributed by shivanisinghss2110                       

C

                         // Log based C program to count number of                       
                         // digits in a number                       
                         #include <math.h>                       
                         #include <stdio.h>                       
           
                         int                                     countDigit(                                     long                                     long                                     n) {                       
                                                 return                                     floor                                     (                                     log10                                     (n) + 1);                       
                         }                       
           
                         // Driver code                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 long                                     long                                     n = 345289467;                       
                                                 printf                                     (                                     "Number of digits : %d"                                     , countDigit(n));                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // JAVA Code to count number of                       
                         // digits in an integer                       
                         import                                     java.util.*;                       
           
                         class                                     GFG {                       
           
                                                 static                                     int                                     countDigit(                                     long                                     n)                       
                                                 {                       
                                                 return                                     (                                     int                                     )Math.floor(Math.log10(n) +                                     1                                     );                       
                                                 }                       
           
                                                 /* Driver code */                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 long                                     n =                                     345289467                                     ;                       
                                                 System.out.print(                                     "Number of digits : "                       
                                                 + countDigit(n));                       
                                                 }                       
                         }                       
                         // This code is contributed by Arnav Kr. Mandal.                       

Python3

                         # Log based Python program to count number of                       
                         # digits in a number                       
           
                         # function to import ceil and log                       
                         import                                     math                       
           
           
                         def                                     countDigit(n):                       
                                                 return                                     math.floor(math.log10(n)                                     +                                     1                                     )                       
           
           
                         # Driver Code                       
                         n                                     =                                     345289467                       
                         print                                     (                                     "Number of digits : % d"                                     %                                     (countDigit(n)))                       
           
                         # This code is contributed by Shreyanshi Arun                       

C#

                         // C# Code to count number of                       
                         // digits in an integer                       
                         using                                     System;                       
           
                         class                                     GFG {                       
           
                                                 static                                     int                                     countDigit(                                     long                                     n)                       
                                                 {                       
                                                 return                                     (                                     int                                     )Math.Floor(Math.Log10(n) + 1);                       
                                                 }                       
           
                                                 /* Driver code */                       
                                                 public                                     static                                     void                                     Main()                       
                                                 {                       
                                                 long                                     n = 345289467;                       
                                                 Console.WriteLine(                                     "Number of digits : "                       
                                                 + countDigit(n));                       
                                                 }                       
                         }                       
           
                         // This code is contributed by anuj_67..                       

PHP

                         <?php                       
                         // Log based php program to                       
                         // count number of digits                       
                         // in a number                       
           
                         function                                     countDigit(                                     $n                                     )                       
                         {                       
                                                 return                                     floor                                     (log10(                                     $n                                     )+1);                       
                         }                       
           
                         // Driver code                       
                         $n                                     = 345289467;                       
                         echo                                     "Number of digits : "                                     ,                       
                                                 countDigit(                                     $n                                     );                       
           
                         // This code is contributed by ajit                       
                         ?>                       

Javascript

                         <script>                       
           
                         // Log based Javascript program to count number of                       
                         // digits in a number                       
                         function                                     countDigit(n)                       
                         {                       
                                                 return                                     Math.floor(Math.log10(n) + 1);                       
                         }                       
           
                         // Driver code                       
                         var                                     n = 345289467;                       
                         document.write(                                     "Number of digits : "                                     +                       
                                                 countDigit(n));                       
                                   
                         // This code is contributed by noob2000                       
           
                         </script>                       

输出

Number of digits : 9

方法4： 我们可以把数字转换成一个字符串，然后找到字符串的长度，得到原始数字的位数。

C++

                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         // To count the no. of digits in a number                       
                         void                                     count_digits(                                     int                                     n)                       
                         {                       
                                                 // converting number to string using                       
                                                 // to_string in C++                       
                                                 string num = to_string(n);                       
           
                                                 // calculate the size of string                       
                                                 cout << num.size() << endl;                       
                         }                       
                         //Driver Code                       
                         int                                     main()                       
                         {                       
                                                 // number                       
                                                 int                                     n = 345;                       
                                                 count_digits(n);                       
                                                 return                                     0;                       
                         }                       
           
                         // This code is contributed by Shashank Pathak                       

JAVA

                         import                                     java.util.*;                       
                         public                                     class                                     GFG {                       
           
                                                 // To count the no. of digits in a number                       
                                                 static                                     void                                     count_digits(                                     int                                     n)                       
                                                 {                       
                                                 // converting number to string using                       
                                                 // to_string in C++                       
                                                 String num = Integer.toString(n);                       
           
                                                 // calculate the size of string                       
           
                                                 System.out.println(+num.length());                       
                                                 }                       
                                                 // Driver code                       
                                                 public                                     static                                     void                                     main(String args[])                       
                                                 {                       
                                                 // number                       
                                                 int                                     n =                                     345                                     ;                       
                                                 count_digits(n);                       
                                                 }                       
                         }                       
                         // Code is contributed by shivanisinghss2110                       

Python3

                         # Python3 implementation of the approach                       
                         def                                     count_digits(n):                       
                                                 n                                     =                                     str                                     (n)                       
                                                 return                                     len                                     (n)                       
           
           
                         # Driver code                       
                         n                                     =                                     456533457776                       
                         print                                     (count_digits(n))                       

C#

                         // C# implementation of the above approach                       
                         using                                     System;                       
                         using                                     System.Collections.Generic;                       
           
                         class                                     GFG {                       
           
                                                 // To count the no. of digits in a number                       
                                                 static                                     void                                     count_digits(                                     int                                     n)                       
                                                 {                       
                                                 // converting number to string using                       
                                                 // to_string in C#                       
           
                                                 string                                     num = Convert.ToString(n);                       
           
                                                 // calculate the size of string                       
                                                 Console.WriteLine(+num.Length);                       
                                                 }                       
           
                                                 // Driver Code                       
                                                 public                                     static                                     void                                     Main(                                     string                                     [] args)                       
                                                 {                       
                                                 // number                       
                                                 int                                     n = 345;                       
                                                 count_digits(n);                       
                                                 }                       
                         }                       
           
                         // This code is contributed by shivanisinghss2110                       

Javascript

                         <script>                       
                                                 // Javascript implementation of the above approach                       
                                   
                                                 // To count the no. of digits in a number                       
                                                 function                                     count_digits(n)                       
                                                 {                       
                                                 // converting number to string using                       
                                                 // to_string in javascript                       
                                   
                                                 let num = n.toString();                       
                                   
                                                 // calculate the size of string                       
                                                 document.write(num.length);                       
                                                 }                       
                                   
                                                 // number                       
                                                 let n = 345;                       
                                                 count_digits(n);                       
                                   
                         </script>                       

输出

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