Leetcode 692. Top K Frequent Words

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.

Example 1:

Input: words = ["i","love","leetcode","i","love","coding"], 

k = 2

Output: ["i","love"]Explanation: "i" and "love" are the two most frequent words. Note that "i" comes before "love" due to a lower alphabetical order.

Example 2:

Input: words = ["the","day","is","sunny","the","the","the","sunny","is","is"], 

k = 4

Output: ["the","is","sunny","day"]Explanation: "the", "is", "sunny" and "day" are the four most frequent words, with the number of occurrence being 4, 3, 2 and 1 respectively.

Constraints:

• 1 <= words.length <= 500

• 1 <= words[i].length <= 10

• words[i] consists of lowercase English letters.

• k is in the range [1, The number of unique words[i]]

map 跟list的联动，以前遇到过类似这个问题，老是记不住。。。

Runtime: 6 ms, faster than 83.47% of Java online submissions for Top K Frequent Words.

Memory Usage: 43.2 MB, less than 16.63% of Java online submissions for Top K Frequent Words.