1 struct cmp 2 { 3     bool operator()(const pair
     
       p1, const pair
      
        p2) 4     { 5         if(p1.second!=p2.second) 6             return p1.second > p2.second; //second的小值优先 7         return p1.first < p2.first; 8     } 9 };10 11 class Solution12 {13     public:14         vector
       
         topKFrequent(vector
        
         & words, int k)15         {16             unordered_map
         
           mymap;17             for(auto s:words)18             {19                 auto ptr_to_str = mymap.find(s);20                 if(ptr_to_str==mymap.end())21                 {22                     mymap.insert(make_pair(s,1));23                 }24                 else25                 {26                     ptr_to_str->second ++;27                 }28             }29 30             priority_queue
          
           
            , vector
            
             
              >, cmp> Q;31 for(auto p:mymap)32 {33 if(Q.size()
              
               Q.top().second || (p.second==Q.top().second && p.first
               
                 result;48 while(!Q.empty())49 {50 result.emplace_back(Q.top().first);51 Q.pop();52 }53 reverse(result.begin(),result.end());54 return result;55 }56 };