【优先队列】LeetCode 692. 前K个高频单词

题目链接

692. 前K个高频单词

思路

还是与前k大问题一样，只不过需要注意一下字典序的问题。

代码

class Solution{
    public List<String> topKFrequent(String[] words, int k){
        HashMap<String, Integer> wordMap = new HashMap<>();
        PriorityQueue<Map.Entry<String, Integer>> wordQueue = new PriorityQueue<>(
                new Comparator<Map.Entry<String, Integer>>(){
                    @Override
                    public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2){
                        if(!o1.getValue().equals(o2.getValue())){
                            return o1.getValue().compareTo(o2.getValue());
                        }

                        return o2.getKey().compareTo(o1.getKey());
                    }
                }
        );
        List<String> res = new ArrayList<>();

        for(String string : words){
            wordMap.put(string, wordMap.getOrDefault(string, 0) + 1);
        }
        for(Map.Entry<String, Integer> entry : wordMap.entrySet()){
            wordQueue.add(entry);
            if(wordQueue.size() > k){
                wordQueue.poll();
            }
        }

        for(int i = 0; i < k; i++){
            res.add(wordQueue.poll().getKey());
        }
        Collections.reverse(res);

        return res;
    }
}