18.longest-palindrome.js

// https://leetcode.com/problems/longest-palindrome/
// Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

// Letters are case sensitive, for example, "Aa" is not considered a palindrome here.

 

// Example 1:

// Input: s = "abccccdd"
// Output: 7
// Explanation: One longest palindrome that can be built is "dccaccd", whose length is 7.
// Example 2:

// Input: s = "a"
// Output: 1
// Explanation: The longest palindrome that can be built is "a", whose length is 1.
 

// Constraints:

// 1 <= s.length <= 2000
// s consists of lowercase and/or uppercase English letters only.

/**
 * @param {string} s
 * @return {number}
 */
 var longestPalindrome = function(s) {
    let hashMap = {};
    for (let i = 0; i < s.length; i++){
        if(!hashMap[s[i]]) {
            hashMap[s[i]] = 1;
        } else {
            hashMap[s[i]]++;
        }
    }
    let ans = 0;
    let middle = false;
    for (const key in hashMap) {
        if (hashMap[key] % 2 === 0) {
            ans += hashMap[key];
        } else {
            if (!middle) {
                ans += 1;
                middle = true;
            }
            
            ans += hashMap[key] - 1;
        }
    }
    return ans
};