medium puzzle

medium.js

// Given a string s, return the longest palindromic substring in s.

 

// Example 1:

// Input: s = "babad"
// Output: "bab"
// Explanation: "aba" is also a valid answer.
// Example 2:

// Input: s = "cbbd"
// Output: "bb"
 

// Constraints:

// 1 <= s.length <= 1000
// s consist of only digits and English letters.

/**
 * @param {string} s
 * @return {string}
 */
var longestPalindrome = function(s) {
    if (s.length === 1) {
        return s;
    }
    
    let longestPalindrome = "";
    
    // Find palendroms starting at center index
    let centeredCreepOutwards = (string, start, end) => {
        let atEdge = false;
        while (atEdge === false && string[start] === string[end]) {
            start -= 1;
            end += 1;
            atEdge = start >= 0 && end < string.length ? false : true;
        }
        return string.slice(start + 1, end);
    }
    

    for (let i = 0; i < s.length - 1; i++) {
        let palindrome = centeredCreepOutwards(s, i, i);
        let twoLetterPalindrome = centeredCreepOutwards(s, i, i + 1);
        if (palindrome.length > longestPalindrome.length) {
             longestPalindrome = palindrome;
        }
        if (twoLetterPalindrome.length > longestPalindrome.length) {
             longestPalindrome = twoLetterPalindrome;
        }
    }
    return longestPalindrome;
};