{"id":917,"date":"2024-10-14T14:05:55","date_gmt":"2024-10-14T08:35:55","guid":{"rendered":"https:\/\/codexplained.in\/?p=917"},"modified":"2025-11-24T15:50:08","modified_gmt":"2025-11-24T10:20:08","slug":"reverse-the-digits-of-a-number-using-recursion","status":"publish","type":"post","link":"https:\/\/codexplained.in\/?p=917","title":{"rendered":"Reverse the Digits of a Number using Recursion"},"content":{"rendered":"\n

Introduction<\/h3>\n\n\n\n

Reversing a number involves changing its digits’ order. For example, reversing 1234<\/code> results in 4321<\/code>. We can achieve this using recursion by isolating the last digit and combining it with the reversed version of the remaining digits.<\/p>\n\n\n

\n#include <stdio.h>\n\nint reverseNumber(int num, int reversed) {\n    \/\/ Base case: if num is 0, return the reversed number\n    if (num == 0) {\n        return reversed;\n    }\n    \/\/ Recursive case: add last digit to reversed number\n    reversed = reversed * 10 + (num % 10);\n    return reverseNumber(num \/ 10, reversed);\n}\n\nint main() {\n    int number;\n    printf("Enter a number: ");\n    scanf("%d", &number);\n\n    int reversed = reverseNumber(number, 0);\n    printf("Reversed number: %d\\n", reversed);\n\n    return 0;\n}\n\n<\/pre><\/div>\n\n\n
Explanation<\/h3>\n\n\n\n
    \n
  1. Function Definition<\/strong>:\n
      \n
    • The function reverseNumber<\/code> takes two parameters: num<\/code> (the number to reverse) and reversed<\/code> (the reversed number so far).<\/li>\n\n\n\n
    • Base Case<\/strong>: If num<\/code> is 0, it returns the reversed<\/code> number, ending the recursion.<\/li>\n\n\n\n
    • Recursive Case<\/strong>:\n
        \n
      • The last digit of num<\/code> is obtained using num % 10<\/code>.<\/li>\n\n\n\n
      • The reversed<\/code> number is updated by multiplying it by 10 (to shift left) and adding the last digit.<\/li>\n\n\n\n
      • The function calls itself with the remaining digits (num \/ 10<\/code>) and the updated reversed<\/code> number.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Main Function<\/strong>:\n
          \n
        • It prompts the user to input a number.<\/li>\n\n\n\n
        • It calls reverseNumber<\/code> with the input number and initializes reversed<\/code> to 0.<\/li>\n\n\n\n
        • Finally, it prints the reversed number.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
          Input and Output Example<\/h3>\n\n\n\n
          Input:<\/strong><\/p>\n\n\n\n
          Enter a number: 1234
          <\/code><\/pre>\n\n\n\n
          Output:<\/strong><\/p>\n\n\n\n
          Reversed number: 4321<\/code><\/pre>\n\n\n\n
          Conclusion<\/h3>\n\n\n\n
          This C program successfully reverses a number using recursion. The recursive approach breaks down the problem by handling one digit at a time, making it easy to understand and implement. While this method is efficient for relatively small numbers, be cautious with large numbers due to potential stack overflow issues with deep recursion.<\/p>\n