用优先队列排序，优先队列是大根堆

 

class Solution {public:    vector
     
       topKFrequent(vector
      
       & nums, int k) {        vector
       
         result;        int length = nums.size();        if(length <= 0)            return result;        unordered_map
        
          m;        priority_queue
         
          
           > n; for(auto a : nums) m[a]++; for(auto a : m) n.push({a.second,a.first}); for(int i = 0;i < k;i++){ result.push_back(n.top().second); n.pop(); } return result; }};
          
         
        
       
      
     

https://www.cnblogs.com/grandyang/p/5454125.html