Answers for "Write code to check a String is palindrome or not?"

check if a string is palindrome cpp

// Check whether the string is a palindrome or not.
#include <bits/stdc++.h>

using namespace std;

int main(){
    string s;
    cin >> s;
    
    int l = 0;
    int h = s.length()-1;

    while(h > l){
        if(s[l++] != s[h--]){
            cout << "Not a palindrome" << endl;
            return 0;
        }
    }
    cout << "Is a palindrome" << endl;
    return 0;

}

check a string is palindrome or not

#include <stdio.h>
#include <string.h>
int main()
{

     char str[80];
     int length;
     printf("nEnter a string to check if it's a palindrome: ");
     scanf("%s", str);     // string input
     length = strlen(str); // finding the string length
     int i, j, count;
     for (i = 0, j = length - 1, count = 0; i < length; i++, j--)
     {
          // matching string first character with the string last character
          if (str[i] == str[j])
          {
               count++; // if character match, increasing count by one.
          }
     }
     if (count == length) // if count == length, then the string is a palindrome.
     {
          printf("'%s' is a palindrome.n", str);
     }
     else // otherwise the string is not a palindrome.
     {
          printf("'%s' is not a palindrome.n", str);
     }
     return 0;
}

reads the string in then determines if the string is a palindrome.

#include <iostream>
using namespace std;
 
// Iterative function to check if given string is a palindrome or not
bool isPalindrome(string str)
{
    int low = 0;
    int high = str.length() - 1;
 
    while (low < high)
    {
        // if mismatch happens
        if (str[low] != str[high])
            return false;
 
        low++;
        high--;
    }
 
    return true;
}
 
int main()
{
    string str = "XYXYX";
 
    if (isPalindrome(str))
        cout << "Palindrome";
    else
        cout << "Not Palindrome";
 
    return 0;
}

find all the palindrome substring in a given string

#include <iostream>
#include <string>
#include <unordered_set>
using namespace std;

// expand in both directions of low and high to find all palindromes
void expand(string str, int low, int high, auto &set)
{
	// run till str[low.high] is a palindrome
	while (low >= 0 && high < str.length()
			&& str[low] == str[high])
	{
		// push all palindromes into the set
		set.insert(str.substr(low, high - low + 1));

		// expand in both directions
		low--, high++;
	}
}

// Function to find all unique palindromic substrings of given string
void allPalindromicSubstrings(string str)
{
	// create an empty set to store all unique palindromic substrings
	unordered_set<string> set;

	for (int i = 0; i < str.length(); i++)
	{
		// find all odd length palindrome with str[i] as mid point
		expand(str, i, i, set);

		// find all even length palindrome with str[i] and str[i+1] as
		// its mid points
		expand(str, i, i + 1, set);
	}

	// print all unique palindromic substrings
	for (auto i : set)
		cout << i << " ";
}

int main()
{
	string str = "google";

	allPalindromicSubstrings(str);

	return 0;
}

check if palindrome

function isPalindrome(str) {
  str = str.toLowerCase();
  return str === str.split("").reverse().join("");
}

reads the string in then determines if the string is a palindrome.

#include <iostream>
using namespace std;
 
// Recursive function to check if str[low..high] is a palindrome or not
bool isPalindrome(string str, int low, int high)
{
    // base case
    if (low >= high)
        return true;
 
    // return false if mismatch happens
    if (str[low] != str[high])
        return false;
 
    // move to next the pair
    return isPalindrome(str, low + 1, high - 1);
}
 
int main()
{
    string str = "XYBYBYX";
    int len = str.length();
 
    if (isPalindrome(str, 0, len - 1))
        cout << "Palindrome";
    else
        cout << "Not Palindrome";
 
    return 0;
}