Top K Frequent Words.md

Given an array of strings words and an integer k, return the k most frequent strings.

Return the answer sorted by the frequency from highest to lowest. Sort the words with the same frequency by their lexicographical order.

/**
 * @param {string[]} words
 * @param {number} k
 * @return {string[]}
 */
//  O(n log n)
var topKFrequent = function(words, k) {
    const map = {};
    for(let word of words) {
        map[word] = map[word] + 1 || 1;
    }
    let res = Object.keys(map).sort((a, b) => {
        let diff = map[b] - map[a];
        if(diff === 0) {
        /*
        sorting descend in an alphabetic order. i.e. a -> b -> c -> d
        localeCompare() returns one of 3 numbers indicating the sort order.
         -1 if sorted before
          1 if sorted after
          0 if equal
        */
            return a.localeCompare(b);
        }
        else {
            return diff;
        }
    })
    return res.slice(0, k);
};