Leecode347 前k个高频元素

class Solution {
public:
    static bool compare(pair<int, int>& m, pair<int, int>& n){
        return m.second > n.second;
    }
    vector<int> topKFrequent(vector<int>& nums, int k) {
        int n = nums.size();
        unordered_map<int, int> record;
        for(auto x : nums){
            record[x]++;
        }
        priority_queue<pair<int, int>, vector<pair<int, int>>, decltype(&compare)> pq(compare);
        for(auto x : record){
            pq.emplace(x);
            if(pq.size() > k){
                pq.pop();
            }
        }
        vector<int> res;
        while(!pq.empty()){
            res.push_back(pq.top().first);
            pq.pop();
        }
        return res;
    }
};