C++ program to check whether a number is Palindrome or not

July 5, 2019

Program to check whether a number is Palindrome or not

Here we will discuss how to check whether a number is palindrome or not using C++ Programming language.

A number is a Palindrome number if the reverse of the number and the numbers itself are equal i.e. if number and its reverse are same then the number is a palindrome number.

Example: Let’s take a number say 2876. Here the reverse of the number is 6782 which is not equal to the number so 2876 is not a palindrome number.

Let’s take another number say 12121. Here the reverse of the number is 12121 which is equal to the number, so 12121 is a Palindrome number.To check for palindrome number we will first reverse the number using a loop and then compare them number and its reverse using the if statement.

Working

Let’s see how the code works:

User gives an input.
Input is stored in an int type variable say num.
num is copied in another int type variable temp
Now using a do while loop the reverse of num will be found.
- Modulus(%) of num is found with 10 and stored in an int type variable say digit.

digit = num%10;

- An int variable reverse(initialised at 0) is multiplied by 10 and digit is added to it and the result is stored in reverse itself.

reverse = (reverse*10) + digit;

- num is divided by 10 and the value is stored in num itself.

num /= 10;

- The loop works until num is not equal to 0.

while(num!=0);

Now reverse will be compared with temp.
If both are equal then the num is Palindrome
Otherwise the num is not a Palindrome.

C++ Code

//C++ Program
//Palindrome or not
#include <iostream>
using namespace std;
//main Program
int main()
{
    int num, digit, reverse = 0;
    cout << "Enter a positive integer: ";
    //user input
    cin >> num;
    int temp = num;
    //loop to find reverse
    do
    {
        digit = num % 10;
        reverse	= (reverse * 10) + digit;
        num = num / 10;
    } while (num != 0);
    cout << "The reverse of "<< temp <<" is "<< reverse << endl;
    //checking for palindrome
    if (temp == reverse)
        cout << "The number is a palindrome.";
    else
        cout << "The number is not a palindrome.";
    return 0;
}

Output

Enter a positive integer: 12121
The reverse of 12121 is 12121
The number is a palindrome.

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