codeforces-solution/1766B.cpp at master · seikhchilli/codeforces-solution · GitHub

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#include<bits/stdc++.h>
using namespace std;


#define ll long long
#define endl "\n"
#define debug(n) cout<<(n)<<endl;
#define pb push_back
const ll INF = 2e18 + 99;

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int t;
  cin>>t;
  while(t--){
    bool flag = false;
    int n;
    cin>>n;
    map<string, int> mp;
    string s;
    cin>>s;
    string a;
    for(int i = 1; i < n; i++){
      a = "";
      a += s[i-1];
      a += s[i];
      if(mp.find(a) != mp.end() && mp[a] < i-1){
        flag = true;
        break;
      }
      else if(mp.find(a) == mp.end()){
        mp[a] = i;
      }

    }
    if(flag) cout<<"YES"<<endl; else cout<<"NO"<<endl;
  }

}