C++ Program to Check if a Given String is Palindrome or Not

// C++ program to check whether the given string
// is palindrome or not using reverse() function
#include <bits/stdc++.h>
using namespace std;

void isPalindrome(string str) {
  
  	// Stores the reverse of the string s
    string rev = str;

    // Reverse the string
    reverse(rev.begin(), rev.end());

    // If rev is equal to str
    if (str == rev)
        cout << "\"" << str
      	<< "\" is palindrome." << endl;
      
	// If rev is NOT equal to str
    else
        cout << "\"" << str
      	<< "\" is NOT palindrome." << endl;
}

int main() {
    
  	// Checking if strings given strings are palindrome
	isPalindrome("ABCDCBA");
  	isPalindrome("ABCD");

    return 0;
}

// C++ program to check whether the string
// is palindrome or not using loop
#include <bits/stdc++.h>
using namespace std;

void isPalindrome (string str) {
  
  	// Specify the starting and ending indexes
    int left = 0, right = str.size() - 1;
  
  	// Flag to terminate the loop if mismatch
  	// characters found
  	bool flag = true;
  	
  	// Till the left is less than right
    while (left < right) {

        // If any character not match, break the
        // loop, string is not palindrome
        if (str[left] != str[right]) {
            flag = false;
            break;
        }
        left++;
        right--;
    }
  	
  	if (flag)
        cout << "\"" << str
      	<< "\" is palindrome." << endl;
      	
    else
        cout << "\"" << str
      	<< "\" is NOT palindrome." << endl;
}
  

int main() {
  
  	// Checking if given strings are palindrome
  	isPalindrome("ABCDCBA");
    isPalindrome("ABCD");            
    return 0;
}

// C++ Prgram to check whether the given string is
// palindrome or not using recursion
#include <iostream>
#include <cstring>
using namespace std;

// Recursive helper function to check if the string
// is a palindrome
bool palinHelper(const string& str, int left,
                 int right) {

    // If the start and end pointers cross each other,
  	// it means all characters have matched
    if (left >= right)
        return true;

    // If characters don't match, the string is not
  	// a palindrome
    if (str[left] != str[right])
        return false;

    // Recursively check for the rest of the string
    return palinHelper(str, left + 1, right - 1);
}

// Function to check if the string is a palindrome
void isPalindrome(string str) {

    // Calling the recursive function to check
  	// palindrome string
    if (palinHelper(str, 0, str.length() - 1))
        cout << "\"" << str << "\" is palindrome."
      		<< endl;
    else
        cout << "\"" << str << "\" is NOT palindrome."
      		<< endl;
}

int main() {
  
    // Checking if the given strings are palindrome
    isPalindrome("ABCDCBA");
    isPalindrome("ABCD");

    return 0;
}