692_Top_K_Frequent_Words.java

class Solution {
    /*public List<String> topKFrequent(String[] words, int k) {
        Map<String, Integer> count = new HashMap();
        for (String word: words) {
            count.put(word, count.getOrDefault(word, 0) + 1);
        }
        List<String> candidates = new ArrayList(count.keySet());
        Collections.sort(candidates, (w1, w2) -> count.get(w1).equals(count.get(w2)) ?
                w1.compareTo(w2) : count.get(w2) - count.get(w1));

        return candidates.subList(0, k);
    }*/
    public List<String> topKFrequent(String[] words, int k) {
        Map<String, Integer> count = new HashMap();
        for (String word: words) {
            count.put(word, count.getOrDefault(word, 0) + 1);
        }
        PriorityQueue<String> heap = new PriorityQueue<String>(
                (w1, w2) -> count.get(w1).equals(count.get(w2)) ?
                w2.compareTo(w1) : count.get(w1) - count.get(w2) );

        for (String word: count.keySet()) {
            heap.offer(word);
            if (heap.size() > k) heap.poll();
        }

        List<String> ans = new ArrayList();
        while (!heap.isEmpty()) ans.add(heap.poll());
        Collections.reverse(ans);
        return ans;
    }
}