atoi（）的递归实现-yiteyi-C++库

这个 atoi（）函数将字符串（表示整数）作为参数并返回其值。

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我们讨论过 atoi（）的迭代实现 .如何递归计算？ 我们强烈建议您尽量减少浏览器，并先自己尝试 其思想是分离最后一个数字，递归计算剩余n-1个数字的结果，将结果乘以10，并将获得的值与最后一个数字相加。下面是这个想法的实施。

C++

                         // Recursive C program to compute atoi()                       
                         #include <stdio.h>                       
                         #include <string.h>                       
           
                         // Recursive function to compute atoi()                       
                         int                                     myAtoiRecursive(                                     char                                     *str,                                     int                                     n)                       
                         {                       
                                                 // Base case (Only one digit)                       
                                                 if                                     (n == 1)                       
                                                 return                                     *str -                                     '0'                                     ;                       
           
                                                 // If more than 1 digits, recur for (n-1), multiply result with 10                       
                                                 // and add last digit                       
                                                 return                                     (10 * myAtoiRecursive(str, n - 1) + str[n-1] -                                     '0'                                     );                       
                         }                       
           
                         // Driver Program                       
                         int                                     main(                                     void                                     )                       
                         {                       
                                                 char                                     str[] =                                     "112"                                     ;                       
                                                 int                                     n =                                     strlen                                     (str);                       
                                                 printf                                     (                                     "%d"                                     , myAtoiRecursive(str, n));                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // Recursive Java program to compute atoi()                       
                         class                                     GFG{                       
           
                         // Recursive function to compute atoi()                       
                         static                                     int                                     myAtoiRecursive(String str,                                     int                                     n)                       
                         {                       
                                   
                                                 // Base case (Only one digit)                       
                                                 if                                     (n ==                                     1                                     )                       
                                                 {                       
                                                 return                                     str.charAt(                                     0                                     ) -                                     '0'                                     ;                       
                                                 }                       
                                   
                                                 // If more than 1 digits, recur for (n-1),                       
                                                 // multiply result with 10 and add last digit                       
                                                 return                                     (                                     10                                     * myAtoiRecursive(str, n -                                     1                                     ) +                       
                                                 str.charAt(n -                                     1                                     ) -                                     '0'                                     );                       
                         }                       
           
                         // Driver code                       
                         public                                     static                                     void                                     main(String[] s)                       
                         {                       
                                                 String str =                                     "112"                                     ;                       
                                                 int                                     n = str.length();                       
                                   
                                                 System.out.println(myAtoiRecursive(str, n));                       
                         }                       
                         }                       
           
                         // This code is contributed by rutvik_56                       

Python3

                         # Python3 program to compute atoi()                       
           
                         # Recursive function to compute atoi()                       
                         def                                     myAtoiRecursive(string, num):                       
                                   
                                                 # base case, we've hit the end of the string,                       
                                                 # we just return the last value                       
                                                 if                                     len                                     (string)                                     =                                     =                                     1                                     :                       
                                                 return                                     int                                     (string)                                     +                                     (num                                     *                                     10                                     )                       
                                   
                                                 # add the next string item into our num value                       
                                                 num                                     =                                     int                                     (string[                                     0                                     :                                     1                                     ])                                     +                                     (num                                     *                                     10                                     )                       
                                   
                                                 # recurse through the rest of the string                       
                                                 # and add each letter to num                       
                                                 return                                     myAtoiRecursive(string[                                     1                                     :], num)                       
           
                         # Driver Code                       
                         string                                     =                                     "112"                       
           
                         print                                     (myAtoiRecursive(string,                                     0                                     ))                       
           
                         # This code is contributed by Frank-Hu-MSFT                       

C#

                         // Recursive C# program to compute atoi()                       
                         using                                     System;                       
                         class                                     GFG{                       
           
                         // Recursive function to compute atoi()                       
                         static                                     int                                     myAtoiRecursive(                                     string                                     str,                                     int                                     n)                       
                         {                       
                                   
                                                 // Base case (Only one digit)                       
                                                 if                                     (n == 1)                       
                                                 {                       
                                                 return                                     str[0] -                                     '0'                                     ;                       
                                                 }                       
                                   
                                                 // If more than 1 digits, recur for (n-1),                       
                                                 // multiply result with 10 and add last digit                       
                                                 return                                     (10 * myAtoiRecursive(str, n - 1) +                       
                                                 str[n - 1] -                                     '0'                                     );                       
                         }                       
           
                         // Driver code                       
                         public                                     static                                     void                                     Main()                       
                         {                       
                                                 string                                     str =                                     "112"                                     ;                       
                                                 int                                     n = str.Length;                       
                                   
                                                 Console.Write(myAtoiRecursive(str, n));                       
                         }                       
                         }                       
           
                         // This code is contributed by Nidhi_Biet                       

Javascript

                         <script>                       
                                                 // Recursive Javascript program to compute atoi()                       
                                   
                                                 // Recursive function to compute atoi()                       
                                                 function                                     myAtoiRecursive(str, n)                       
                                                 {                       
           
                                                 // Base case (Only one digit)                       
                                                 if                                     (n == 1)                       
                                                 {                       
                                                 return                                     str[0].charCodeAt() -                                     '0'                                     .charCodeAt();                       
                                                 }                       
           
                                                 // If more than 1 digits, recur for (n-1),                       
                                                 // multiply result with 10 and add last digit                       
                                                 return                                     (10 * myAtoiRecursive(str, n - 1) + str[n - 1].charCodeAt() -                                     '0'                                     .charCodeAt());                       
                                                 }                       
                                   
                                                 let str =                                     "112"                                     ;                       
                                                 let n = str.length;                       
                                   
                                                 document.write(myAtoiRecursive(str, n));                       
           
                         // This code is contributed by decode2207.                       
                         </script>                       

输出：

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