求一个字符串中连续出现次数最多的子串

C++
使用hash map存储每个子串出现的次数
 1 #include <iostream>
 2 #include <vector>
 3 #include <unordered_map>
 4 using namespace std;
 5 
 6 pair<int, string> fun(const string& str) {
 7     int len = str.length();
 8     if (len == 0){
 9         return make_pair(0,string(""));
10     }
11     unordered_map<string, int> map(len*len);
12 
13     pair<int, string> ret = make_pair(1, str.substr(0,1));
14 
15     for (int i = 0; i < len; ++i) {
16         for (int j = 1; j < len - i + 1; ++j) {
17             string substr = str.substr(i,j);
18             if (map.find(substr) == map.end()) {
19                 map[substr] = 1;
20             } else {
21                 map[substr] += 1;
22                 if (map[substr] > ret.first) {
23                     ret = make_pair(map[substr], substr);
24                 } else if (map[substr] == ret.first && substr.length() > ret.second.length()) {
25                     ret = make_pair(map[substr], substr);
26                 }
27             }
28         }
29     }
30     return ret;
31 };
32 int main()
33 {
34     string str = "zhanghaeha";
35     pair<int, string> rs = fun(str);
36     cout<<rs.second<<":"<<rs.first<<endl;
37     return 0;
38 }