347. 前 K 个高频元素

 1 class Solution 
 2 {
 3 public:
 4     vector<int> topKFrequent(vector<int>& nums, int k) 
 5     {
 6         vector<int> res;
 7         unordered_map<int,int> hash;
 8         for(auto a : nums) hash[a] ++;
 9         priority_queue<pair<int,int>> pq;
10         for(auto a : hash) pq.push({a.second,a.first});
11         while(k --)
12         {
13             if(!pq.empty())
14             {
15                 res.push_back(pq.top().second);
16                 pq.pop();
17             }
18         }
19         return res;
20     }
21 };