求一个字符串中连续出现次数最多的子串

例如字符串“abababc”,最多连续出现的为ab，连续出现三次。

求一个字符串中连续出现的次数最多的子串，首先生成后缀数组例如

abababc
bababc
ababc
babc
abc
bc
c

这题跟 

后缀数组求最长重复子串 一样都用到了后缀数组。

#include<iostream>
#include<string>
#include<vector>
using namespace std;


pair<int, string> fun(string str){
  int len = str.size();
  vector<string> subs(len);
  for (int i = 0; i < len; i++){
    subs[i] = str.substr(i, len - i);
  }
  int maxSub=0;
  string res;
  for (int i = 0; i < len; i++){
    for (int j = i + 1; j < len; j++){
      int cnt = 1;
      if (subs[i].substr(0, j - i) == subs[j].substr(0, j - i)){
        cnt++;
        for (int k = j + (j - i); k < len; k += j - i){
          if (subs[i].substr(0, j - i) == subs[k].substr(0, j - i)){
            cnt++;
          }
          else{
            break;
          }
        }
        if (cnt>maxSub){
          maxSub = cnt;
          res = subs[i].substr(0, j - i);
        }
      }
    }
  }
  return make_pair(maxSub, res);
}

int main(){
  string str = "abababc";
  pair<int, string> res = fun(str);
  cout << res.first << endl;
  cout << res.second << endl;

  return 0;
}