In this article, we are given a string, our task is to find string is palindrome or not. A palindrome is a series of numbers, strings, or letters that, when read from right to left and left to right, match each other exactly or produce the same series of characters. in simple words when number strings or characters are inverted and still provide the same outcome as the original numbers or characters.
Example:
Input : "race"
Output : passed string is not a palindrome
Explanation : if we write "race" in reverse that is "ecar" it not
matches with first string so it is not a palindrome.
Example 2:
Input : "hellolleh"
Output : passed string is palindrome.
These are the following methods by which we can check whether a passed string is palindrome or not:
- By using a Naive Approach
- By reversing the string
- Uses the split(), reverse(), and join() Methods
Approach 1: By using a Naive Approach
In this approach, we use the following steps.
- First, we iterate over a string in forward and backward directions.
- Check if all forward and backward character matches, and return true.
- If all forward and backward character does not matches, return false.
- If a return is true, it is a palindrome.
Example: This example shows the use of the above-explained approach.
Javascript
// function that check str is palindrome or not function check_palindrome(str) { let j = str.length - 1; for (let i = 0; i < j / 2; i++) { let x = str[i];//forward character let y = str[j - i];//backward character if (x != y) { // return false if string not match return false; } } /// return true if string is palindrome return true;}//function that print output if string is palindromefunction is_palindrome(str) { // variable that is true if string is palindrome let ans = check_palindrome(str); //condition checking ans is true or not if (ans == true) { console.log("passed string is palindrome "); } else { console.log("passed string not a palindrome"); }}// test variablelet test = "racecar";is_palindrome(test); |
Output :
passed string is palindrome.
Approach 2: By reversing the string
Another approach is to reverse a string and check if the initial string matches the reverse string or not.
Follow the following steps :
- Initialize reverse_str a variable that stores the reverse of the passed string.
- Compare the string to reverse_str.
- If matches, it is a palindrome.
- The else string is not a palindrome.
Example: This example shows the use of the above-explained approach.
Javascript
// function to reverse the stringfunction reverse(str) { // variable holds reverse string let rev_str = ""; for (let i = str.length - 1; i >= 0; i--) { rev_str += str[i]; } // return reverse string return rev_str;}// function checking string is palindrome or not function is_palindrome(str) { reverse_str = reverse(str); // condition checking if reverse str is // same as string it is palindrome // else not a palindrome if (reverse_str === str) { console.log("passed string is palindrome "); } else { console.log("passed string is not palindrome") }}let test = "hellolleh";is_palindrome(test); |
Output :
passed string is palindrome.
Approach 3: Uses the split(), reverse(), and join() Methods
Another approach, which is through the shortest approach, uses the split(), reverse(), and join() methods.
- Split the string of characters into several different characters (which is though unsorted at the moment).
- Use the reverse() method to reverse all the characters of the string alphabetically.
- Then apply the join() method in order to join all the characters of the string (which are now sorted).
Example: Below is the implementation of the above approach:
Javascript
// JavaScript code in order to check string palindrome...let checkPalindrome = (stringg) => { return stringg === stringg.split("").reverse().join("");};console.log("Is Palindrome? : " + checkPalindrome("noon"));console.log("Is Palindrome?: " + checkPalindrome("apple")); |
Output:
Is Palindrome? : true
Is Palindrome?: false
