692. 前K个高频单词

692. 前K个高频单词

class Solution {
    public List<String> topKFrequent(String[] words, int k) {
        List<String> ans = new ArrayList<>();
        // 单词频率统计
        Map<String, Integer> map = new HashMap<>();
        for (String word : words) {
            if (!map.containsKey(word)) {
                map.put(word, 1);
            } else {
                map.put(word, map.get(word) + 1);
            }
        }
        // 出现次数相同时按照字母顺序进行排序，出现次数不同时按照频率进行排序；
        PriorityQueue<String> minHeap = new PriorityQueue<>(
            (o1, o2) -> (map.get(o1) == map.get(o2) ? o2.compareTo(o1) : map.get(o1) - map.get(o2))
        ); 
        for (String word : map.keySet()) {
            minHeap.offer(word);
            if (minHeap.size() > k)
                minHeap.poll();
        }
        for (int i = 0; i < k; i++) {
            ans.add(minHeap.remove());
        }
        Collections.reverse(ans);
        return ans;
    }
}