leetcode 347.前k个高频元素

class Solution {
public:
    class myCmp{
    public:
        bool operator()(const pair<int,int>&l,const pair<int,int>& r ){
            return l.second>r.second;
        }
    };

    vector<int> topKFrequent(vector<int>& nums, int k) {
        unordered_map<int,int> mpt;
        for(int i=0;i<nums.size();i++){
            mpt[nums[i]]++;
        }
        
        
        priority_queue<pair<int,int>,vector<pair<int,int>>,myCmp> q;
        for(auto it:mpt){
            q.push(it);
            if(q.size()>k){
                q.pop();
            }
        }
        vector<int> res(k);
        for(int i=k-1;i>=0;i--){
            res[i]=q.top().first;
            q.pop();
        }
        return res;

    }
};

优先队列的应用