比如：“yyabcdabjcabceg"，输出结果应该为abc 和3.
#include<iostream>
#include<string>
using namespace std;
int main()
{
string str, tep;
cout << "输入字符串" << endl;
cin >> str;
for (int i = str.length() - 1; i > 1; i--)
{
for (int j = 0; j < str.length(); j++)
{
if (j + i <= str.length())
{
size_t t = 0;
size_t num = 0;
tep = str.substr(j, i);//从大到小取子串
t = str.find(tep);//正序查找
num = str.rfind(tep);//逆序查找
if (t != num)//假设两次查找位置不一致，说明存在反复子串
{
cout << tep << " " << t + 1 << endl;//输出子串及位置
system("pause");
return 0;
}
}
}
}
}