C Program to check whether the given number is a Palindrome or Not

Arushi Dwivedi | February 16, 2021 | C Programming Example | No Comments

In this C Programming example, we will implement the program to check whether the given number is a Palindrome or not by using the user’s input and print it on screen. We will implement the program using loops and recursive functions.

Table of Contents

1. Palindrome number

A Palindrome is a word, string, number or any sequence that reads same forward and backward.

A Palindromic number is a number that reads the same when the digits are read backward (such as 121 or 11211).

Helpful topics to understand this program better are

2. Palindrome program in C using Loop

Let’s discuss the execution(kind of pseudocode) for the program to find whether a string is a Palindrome or not in C.

In the first step of the program, the number(integer) is entered by the user and is stored in a temporary variable i.e. x.
This temporary variable is equal to the originalNumber.
The originalNumber is then reversed and is stored in the reversedNumber variable.
The next step is to compare both the variables i.e. originalNumber and reversedNumber.
If both numbers are the same, print it as a palindrome number. Else print not a palindrome number.

Let us implement this concept in the c program and check whether the given number is Palindrome or not.

#include <stdio.h>
int main() {
    int x, reversedNumber = 0, remainder, originalNumber;
    printf("Enter an integer: ");
    scanf("%d", &x);
    originalNumber = x;

    // reversed integer is stored in reversedNumber
    while (x != 0) {
        remainder = x % 10;
        reversedNumber = reversedNumber * 10 + remainder;
        x /= 10;
    }

    // condition is checked if the given number is palindrome or not.
    if (originalNumber == reversedNumber)
        printf("%d is a palindrome.", originalNumber);
    else
        printf("%d is not a palindrome.", originalNumber);

    return 0;
}

Output
Testing for integer...
Enter an integer: 121
121 is a palindrome.

3. Palindrome number program in C using Recursion

In the last section, we have implemented a program using loops, let’s now use the Recursive approach to validate if the given number is a Palindrome or not.

In this, we use recursion to find the reverse of a number and then compare the reversedNumber with the originalNumber to validate if the number is a Palindrome or not.

#include <stdio.h>
#include <math.h>

int reverse(int number);
int isPalindrome(int number);

int main()
{
    int number;

    //Input is entered by the user
    printf("Enter an Integer:");
    scanf("%d", &number);

    //Condition is verified for a number to be a palindrome or not
    if (isPalindrome(number) == 1)
    {
        printf("%d is a Palindrome number.\n", number);
    }
    else
    {
        printf("%d is not Palindrome number.\n", number);
    }
    return 0;
}

//Recursive function to find reverse of any number
int reverse(int number)
{
    //Finding the number of digits in numbers
    int digits = (int)log10(number);
    if (number == 0)
        return 0;

    return ((number % 10 * pow(10, digits)) + reverse(number / 10));
}

// Function to verify whether a number is a palindrome or not.
// This function returns 1 if the number is palindrome or else it will return 0.
int isPalindrome(int number)
{
    //Check if the given number is equal to its reverse.

    if (number == reverse(number))
    {
        return 1;
    }
    return 0;
}

Output
Testing for integer...
Enter an Integer:12321
12321 is a Palindrome number.

4. Conclusion

In this C Programming example, we have discussed how to check whether the given number is Palindrome or not via two different approaches, using a loop and using recursive functions, and finally, print the result to the console.

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