5. Longest Palindromic Substring

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

Example 1:

Input: "babad"
Output: "bab"
Note: "aba" is also a valid answer.

Example 2:

Input: "cbbd"
Output: "bb"

/**
 * @param {string} s
 * @return {string}
 */
var longestPalindrome = function(s) {
    let result = '';
    let start;
    let end;
    outer:
    for (let mid = 0; mid < s.length; mid += 0.5) {
        for (let i = Math.floor(mid), j = Math.round(mid); i >= 0, j <= 2 * mid; i--, j++) {
            if (s[i] !== s[j]) {
                break;
            }
            start = i;
            end = j;
        }
        let len = end - start + 1;
        if (len > result.length) {
            result = s.substring(start, end + 1);
        }
    }
    return result;
};

/**
 * @param {string} s
 * @return {string}
 */
var longestPalindrome = function(s) {
    const size = s.length;
    if (size < 2) {
        return s;
    }
    let start = 0;
    let end = 0;
    let i;
    let j;
    const checkPalindrome = function(mid1, mid2) {
        i = mid1;
        j = mid2;
        for (; i >= 0, j < size; i--, j++) {
            if (s[i] !== s[j]) {
                break;
            }
        }
        if ((j - i - 1) > (end - start)) {
            start = i + 1;
            end = j - 1;
        }
    }
    for (let mid = 0; mid < size - 1; mid++) {
        checkPalindrome(mid, mid);
        if (s[mid] === s[mid + 1]) {
            checkPalindrome(mid, mid + 1);
        }
    }
    return s.substring(start, end + 1);
};