check_if_a_string_is_a_palindrome.md

Check if a String is a Palindrome

Check if a String is a Palindrome

A palindrome is a word, phrase, or sequence that reads the same backward as forward.

Algorithm:

1. Remove all non-alphanumeric characters and convert the string to lowercase to handle case sensitivity.
2. Use two pointers: one starting at the beginning and the other at the end of the string.
3. Compare characters at the two pointers. If they differ, the string is not a palindrome.
4. Move the pointers closer to the center and repeat the comparison.
5. If all characters match, the string is a palindrome.

Example:

function isPalindrome(str) {
    // Normalize the string: remove non-alphanumeric characters and convert to lowercase
    const cleanStr = str.replace(/[^a-zA-Z0-9]/g, '').toLowerCase();

    let left = 0;
    let right = cleanStr.length - 1;

    while (left < right) {
        if (cleanStr[left] !== cleanStr[right]) {
            return false; // Not a palindrome
        }
        left++;
        right--;
    }

    return true; // It's a palindrome
}

// Example usage
console.log(isPalindrome("A man, a plan, a canal, Panama")); // Output: true
console.log(isPalindrome("hello")); // Output: false

This method has a time complexity of O(n), where n is the length of the string.

Tags: basic, JavaScript, Strings, Algorithm

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