1 struct cmp
2 {
3 bool operator()(const pair<string,int> p1, const pair<string,int> 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 Solution
12 {
13 public:
14 vector<string> topKFrequent(vector<string>& words, int k)
15 {
16 unordered_map<string,int> 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 else
25 {
26 ptr_to_str->second ++;
27 }
28 }
29
30 priority_queue<pair<string,int>, vector<pair<string,int>>, cmp> Q;
31 for(auto p:mymap)
32 {
33 if(Q.size()<k)
34 {
35 Q.push(make_pair(p.first,p.second));
36 }
37 else
38 {
39 if(p.second>Q.top().second || (p.second==Q.top().second && p.first<Q.top().first))
40 {
41 Q.pop();
42 Q.push(make_pair(p.first,p.second));
43 }
44 }
45 }
46
47 vector<string> 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 };
