Write a program to reverse a number in c

In this post, you will learn how to reverse a number in C programming language. These are different ways to reverse a number in C.

Reverse a number in C using while loop

In the given C program, we have used the while loop to find the reverse of the given number. This program takes user input and loop until num != 0 is false (0) -

#include <stdio.h>
int main() {
    int num, rev = 0, rem;
    printf("Please enter an integer : ");
    scanf("%d", &num);
    while (num != 0) {
        rem = num % 10;
        rev = rev * 10 + rem;
        num /= 10;
    }
    printf("Reverse of entered number %d", rev);
    return 0;
}

Please enter an integer: 52434
Reverse of entered number 43425

Reverse a number in C using recursion

Recursion function is a function which is call itself. In the given example, we call the recursion function to get the reverse of a number. A recursion function continues until some condition is met to prevent it. That's why, we use the if statement to break the infinite recursion. In the given C program, we have used recursion to reverse a given number -

#include <stdio.h>
long reverse(long);

int main()
{
   long num, rev;
   printf("Please enter an integer : ");
   scanf("%ld", &num);
   rev = reverse(num);
   printf("Reverse of entered number : %ld\n", rev);
   return 0;
}

long reverse(long num) {
   static long rev = 0;

   if(num == 0)
      return 0;

   rev = rev * 10;
   rev = rev + num % 10;
   reverse(num/10);
   return rev;
}

Please enter an integer : 423222
Reverse of entered number : 222324

Reverse a number in C using for loop

In the given example, we have used the for loop to find the reverse of the given number.

// Reverse a number in C using for loop
#include<stdio.h>

void main(){
    int num, rev_num=0, remainder, x; 
    printf("Enter the number to reverse: ");

    scanf("%d",&num);

    x = num;
    for(;num>0;){
        remainder = num%10;
        rev_num = rev_num*10+remainder;
        num = num/10;
    }
    printf("Reverse of %d is %d",x,rev_num);
}

Enter the number to reverse: 876234
Reverse of 876234 is 432678

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