D. Peculiar Movie Preferences

#include<iostream>
#include<vector>
#include<map>
#include<algorithm> 
#include<bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
typedef pair<int, int> PII;
typedef long long ll;


int n;
void solve() {
  cin >> n;
  map<string, int> f2, f3, h3;
  bool f = 0;
  for (int i = 1; i <= n; i ++) {
    string s;
    cin >> s;
    string rrr =s;
          reverse(rrr.begin(), rrr.end());
          if (rrr == s) f = 1;
    if (s.size() == 1) {
      f = 1;
    }
    else if (s.size() == 2) {
      string rs = s;
      reverse(rs.begin(), rs.end());
      if (f2[rs] || f3[rs]) f = 1;
      f2[s] = 1;
    } 
    else {
          
      string rs = s;
      reverse(rs.begin(), rs.end());
      if (h3[rs]) f = 1;
      string rs2 = s.substr(1, 2);
      reverse(rs2.begin(), rs2.end());
      if (f2[rs2]) f =1; 
      string rs22 = s.substr(0, 2);
      h3[s] = f3[rs22] = 1;
    }
  } 
  if (f) puts("YES");
  else 
  puts("NO");
}
int main ()  {
  int t;
  cin >>t;
  while (t --) solve();
  return 0;
} 

分类讨论的重要性。这里一眼看过去的时候觉得一大坨，非常难搞。这时候应该对长度进行分类讨论，长度