[leetcode]692. Top K Frequent Words

Analysis

normal day—— [每天刷题并不难0.0]

Given a non-empty list of words, return the k most frequent elements.
Your answer should be sorted by frequency from highest to lowest. If two words have the same frequency, then the word with the lower alphabetical order comes first.

Implement

对PQ来说，如果想要维持大顶堆（即对头元素最大），则应该重载<号；反之对于小顶堆，应该重载>号

class Solution {
public:
    vector<string> topKFrequent(vector<string>& words, int k) {
        vector<string> res;
        unordered_map<string, int> cnt;
        for(string w:words)
            cnt[w]++;
        priority_queue<pair<string, int>, vector<pair<string, int>>, cmp> pq(cnt.begin(), cnt.end());
        while(k--){
            res.push_back(pq.top().first);
            pq.pop();
        }
        return res;
    }
private:
    struct cmp{
        bool operator()(const pair<string, int>& p1, const pair<string, int>& p2){
            if(p1.second == p2.second)
                return p1.first > p2.first;
            return p1.second < p2.second;
        }
    };
};