C Program: Palindrome check using While loop

Last update on July 29 2025 12:58:34 (UTC/GMT +8 hours)

9. Palindrome Number Check Using a While Loop

Write a C program that implements a program to check if a given number is a palindrome using a while loop.

Sample Solution:

C Code:

#include <stdio.h>

int main() {
    int num, reversedNum = 0, originalNum;  // Declare variables for the number, reversed number, and original number

    printf("Input a number: ");
    scanf("%d", &num);  // Read the input number from the user
    originalNum = num;  // Store the original number for comparison later

    // Start a while loop to reverse the digits of the number
    while (num != 0) {
        int remainder = num % 10;  // Extract the last digit
        reversedNum = reversedNum * 10 + remainder;  // Build the reversed number
        num /= 10;  // Remove the last digit from the original number
    }

    // Check if the reversed number is equal to the original number
    if (originalNum == reversedNum) {
        printf("%d is a palindrome.\n", originalNum);
    } else {
        printf("%d is not a palindrome.\n", originalNum);
    }

    return 0;  // Indicate successful program execution
}

Sample Output:

Input a number: 12345
12345 is not a palindrome.

Input a number: 1111
1111 is a palindrome.

Input a number: 5665
5665 is a palindrome.

Explanation:

Here are key parts of the above code step by step:

User Input:

Prompts the user to input a number.
Reads the input and stores it in the variable 'num'.

Variable Initialization:

Initializes variables 'reversedNum' and 'originalNum'.
reversedNum will store the reversed digits of the input number.
originalNum preserves the original input for later comparison.

While Loop (Digit Reversal):

Enters a while loop that continues until the original number becomes 0.
Inside the loop, extracts the last digit of 'num'.
Builds the reversed number ('reversedNum') by appending the extracted digit.
Removes the last digit from the original number ('num').

Palindrome Check:

Compares the original number ('originalNum') with the reversed number (reversedNum).
Prints whether the original number is a palindrome or not.

Return Statement:

Indicates successful program execution.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to check if a given integer is a palindrome using a while loop without converting it to a string.
Write a C program to determine if a number is a palindrome using a while loop and a recursive function to reverse the digits.
Write a C program to check for a palindrome by comparing the original number with its reversed form computed in a while loop.
Write a C program to check if a number is a palindrome using a while loop and then display both the original and reversed numbers.

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C Programming Code Editor:

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