TopKFrequentWords.java

import java.util.*;

class Solution {
    public List<String> topKFrequent(String[] words, int k) {
        Map<String, Integer> map = new HashMap<>();
        for(String word: words) {
            map.put(word, map.getOrDefault(word, 0)+1);
        }
        
        PriorityQueue<String> pq = new PriorityQueue<>(new Comparator<String>() {
            public int compare(String word1, String word2) {
                int freq1 = map.get(word1);
                int freq2 = map.get(word2);
                if (freq1 == freq2) return word2.compareTo(word1);
                return freq1 - freq2;
            }
        });
         
        for(Map.Entry<String, Integer> entry: map.entrySet()) {
            pq.add(entry.getKey());
            if (pq.size() > k) {
                pq.poll();
            }
        }
        
        List<String> result = new ArrayList<>();
        while (!pq.isEmpty()) result.add(pq.poll());
        
        Collections.reverse(result);
        return result;
    }
}

//O(NlogK)