C program to check whether a number is palindrome or not

In this post, you will learn how to write a C program to check whether a number is a palindrome or not.

A Palindrome is a number, string, or sequence that remains the same when it is reversed. A palindrome sequence can be a combination of digits or numbers, but it looks the same in forward and backward. It is generally used where recreational mathematics is applied, like puzzles, games. To check whether a number or string is palindrome or not, simply reverse it and compare it with the original number or string. If both are same, then the number or string is a palindrome, otherwise not.

121, 1991, 1239321, MAAM, DAD, WOW

When we reverse the above numbers or strings, they will remain the same. So, all the above are palindrome.

C program to check palindrome using while loop

In the given C program, first we ask the user to enter a number. Then, we generate a new number by reversing the original number. Next, we have checked if the original number and reversed number are the same. The number is a palindrome.

// C program to check palindrome
#include <stdio.h>
int main()
{
   int num, rev_num=0, remainder, temp;
   printf("Please enter an integer: ");
   scanf("%d", &num);

   /* Generating new number by reversing
    the original number */

   temp=num;
   while(temp!=0)
   {
      remainder=temp%10;
      rev_num=rev_num*10+remainder;
      temp/=10;
   }

   // check both original number and reverse number
   if(rev_num==num)
      printf("%d is a palindrome number.",num);
   else
      printf("%d is not a palindrome number.",num);
   return 0;
}

Please enter an integer: 45654
45654 is a palindrome number.

Please enter an integer: 1223221
1223221 is a palindrome number.

C program to check palindrome using recursion

A recursion function is a function that is called itself. In the given example, we call the recursion function to check the palindrome. A recursion function continues until some condition is met to prevent it. That's why, we use the if else statement to break the infinite recursion. Here, we have used a user-defined recursion function is_palindrome() to check whether the given number is palindrome or not.

#include<stdio.h>

int is_palindrome(int num){

   static int rev_num=0,rem;

   if(num!=0){
      rem = num%10;
      rev_num = rev_num*10+rem;
      is_palindrome(num/10);
   }

   return rev_num;
}
int main(){
   int num, rev_num;

   printf("Please enter a number : ");
   scanf("%d",&num);

   rev_num = is_palindrome(num);

   if(num == rev_num)
      printf("%d is a palindrome number.",num);
   else
      printf("%d is not a palindrome number.",num);

   return 0;
}

Please enter a number : 4566654
4566654 is a palindrome number.

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