/*

* @lc app=leetcode id=692 lang=cpp

*

* [692] Top K Frequent Words

*/

class Solution

{

public:

vector<string> topKFrequent(vector<string> &words, int k)

{

vector<string> res;

unordered_map<string, int> m;

auto comp = [](pair<int, string> &a, pair<int, string> &b) {

// first为出现次数，second为字母顺序排列

return a.first == b.first ? a.second < b.second : a.first > b.first;

};

priority_queue<pair<int, string>, vector<pair<int, string>>, decltype(comp)> pq(comp);

for (auto x : words)

{

m[x]++;

}

for (auto x : m)

{

pq.push({x.second, x.first});

if (pq.size() > k)

pq.pop();

}

while (!pq.empty())

{

res.push_back(pq.top().second);

pq.pop();

}

reverse(res.begin(), res.end());

return res;

}

};