can somebody tell why below code for problem BINSTRING from starters 27 is showing **TLE**

even when it has O(N) time complexity?

**APPROACH: **

I created every possible string that can be created by indexes and kept track of them using a map.since i am storing boolean values corresponding to each string,the size of map will give the number of distinct binary strings.

**CODE**

```
#include "bits/stdc++.h"
#define ll long long int
#define MOD 1000000007
using namespace std;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t;
cin >> t;
while (t--)
{
ll n;
cin >> n;
string s;
cin >> s;
map<string,bool> mp;
string dummy;
ll ans=0;
for(ll i=0;i<s.length();i++)
{
if(i==0)
dummy=s.substr(1,s.length()+1);
else if(i==n)
dummy=s.substr(0,n);
else
dummy=s.substr(0,i)+s.substr(i+1,n+1);
mp[dummy]=true;
}
for(auto it:mp)
{
if(it.second==true)
ans++;
}
cout<<ans<<endl;
}
return 0;
}
```