347. Top K Frequent Elements.md

class Solution {
public:
    vector<int> topKFrequent(vector<int>& nums, int k) {
        unordered_map<int, int> m;
        priority_queue<pair<int, int>> pq;
        vector<int> res;
        for (int num : nums) {
            m[num]++;
        }
        for (auto it : m) {
            pq.push({it.second, it.first});
        }
        for (int i = 0; i < k; ++i) {
            res.push_back(pq.top().second);
            pq.pop();
        }
        return res;
    }
};

class Solution {
public:
    vector<int> topKFrequent(vector<int>& nums, int k) {
        unordered_map<int, int> hm;
        for (auto num : nums) 
            hm[num]++;
        priority_queue<pair<int, int>> pq;
        vector<int> res;
        int n = hm.size();
        for (auto it = hm.begin(); it != hm.end(); ++it) {
            pq.push(make_pair(it->second, it->first));
            if (pq.size() > n - k) {
                res.push_back(pq.top().second);
                pq.pop();
            }
        }
        return res;
    }
};