C Program to Find Reverse of a Number using Recursion

Problem Description

This C program finds the reverse of a number using recursion.

Problem Solution

The following C program using recursion reverses the digits of the number and displays it on the output of the terminal. Eg: 123 becomes 321.

Program/Source Code

#include <stdio.h>
#include <math.h>
 
int rev(int, int);
 
int main()
{
    int num, result;
    int length = 0, temp;
 
    printf("Enter an integer number to reverse: ");
    scanf("%d", &num);
    temp = num;
    while (temp != 0)
    {
        length++;
     ....Show More

Problem Description

This C program finds the reverse of a number using recursion.

Problem Solution

The following C program using recursion reverses the digits of the number and displays it on the output of the terminal. Eg: 123 becomes 321.

Program/Source Code

#include 
#include 
 
int rev(int, int);
 
int main()
{
    int num, result;
    int length = 0, temp;
 
    printf("Enter an integer number to reverse: ");
    scanf("%d", &num);
    temp = num;
    while (temp != 0)
    {
        length++;
        temp = temp / 10;
    }
    result = rev(num, length);
    printf("The reverse of %d is %d.\n", num, result);
    return 0;
}
 
int rev(int num, int len)
{
    if (len == 1)
    {
        return num;
    }
    else
    {
        return (((num % 10) * pow(10, len - 1)) + rev(num / 10, --len));
    }
}

Program Explanation

In this C program, we are reading the integer number using the num variable. Assign the value of num variable to temp variable. While loop is used to check the condition the value of temp variable is not equal to 0, if the condition is true execute the statement divide the value of temp variable by 10.

The result variable is used to call the rev() function by passing num and length variable value as argument. The function rev() is used to reverse the digits of the number. If else condition statement is used to check the value of len variable is equal to 1. If the condition is true execute the statement.

Otherwise, if the condition is false execute the statement. Compute the modulus of the value of num variable by 10 integer and multiply the resulted value with 10. Compute the power of the value of len variable using pow() function. Add the resulted value num variable with 10. Print the reverse of a number using recursion.

Output:

Enter an integer number to reverse: 1234

The reverse of 1234 is 4321.