Check if the given string is Palindrome or not in C++

Understanding Palindrome

A palindrome is a string that reads the same forward and backward.

We will explore three different methods to check if a string is a palindrome using C++.

Method 1: Using a Loop

This method iterates through the string and checks if it is a palindrome.

#include <iostream>
#include <algorithm>
using namespace std;

bool isPalindrome(string str) {
    int l = 0, r = str.length() - 1;
    while (l < r) {
        if (str[l] != str[r])
            return false;
        l++, r--;
    }
    return true;
}

int main() {
    string str = "madam";
    if (isPalindrome(str))
        cout << "Palindrome" << endl;
    else
        cout << "Not a Palindrome" << endl;
    return 0;
}
            

Method 2: Using Recursion

This method checks palindrome property recursively.

#include <iostream>
#include <algorithm>
using namespace std;

bool isPalindromeRecursive(string str, int l, int r) {
    if (l >= r) return true;
    if (str[l] != str[r]) return false;
    return isPalindromeRecursive(str, l + 1, r - 1);
}

int main() {
    string str = "racecar";
    if (isPalindromeRecursive(str, 0, str.length() - 1))
        cout << "Palindrome" << endl;
    else
        cout << "Not a Palindrome" << endl;
    return 0;
}
            

Method 3: Using String Reverse

This method reverses the string and compares it with the original.

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    string str = "hello", rev = str;
    reverse(rev.begin(), rev.end());
    if (str == rev)
        cout << "Palindrome" << endl;
    else
        cout << "Not a Palindrome" << endl;
    return 0;
}