不是双指针 想知道哪里错了

解题思路:

注意事项:

参考代码:

#include<bits/stdc++.h>

using namespace std;

int main()

{

int flag = 0;

string s1,s2;

cin >> s1;

s2 = s1[0];

int ans = 0,maxx = 0;

for(int i = 1 ; i < s1.size();i++)

{

char c = s1[i];

if(s2.find(c) == string::npos && i+1 != s1.size())

{

s2 += s1[i];

}

else

{

if(i+1 == s1.size() && s2.find(c) == string::npos)

flag = 1;

int pos = s2.find(c);

ans = s2.size();

if(ans > maxx)

maxx = ans;

s2 = s2.erase(0,pos+1);

s2 += c;

}

}

if(flag == 1)

cout << maxx+1;

else cout << maxx;

return 0;

}