description: A string is called square if it is some string written twice in a row. For example, the strings "aa", "abcabc", "abab" and "baabaa" are square. But the strings "aaa", "abaaab" and "abcdabc" are not square.
  
  For a given string s determine if it is square.
  
  Input
  
  The first line of input data contains an integer t (1 ≤ t ≤ 100) —the number of test cases.
  
  This is followed by t lines, each containing a description of one test case. The given strings consist only of lowercase Latin letters and have lengths between 1 and 100 inclusive.
  
  Output
  
  For each test case, output on a separate line:
  
    * YES if the string in the corresponding test case is square, 
    * NO otherwise. 
  
  
  
  You can output YES and NO in any case (for example, strings yEs, yes, Yes and YES will be recognized as a positive response).
  
  Example
  
  Input
  
  
  10
  a
  aa
  aaa
  aaaa
  abab
  abcabc
  abacaba
  xxyy
  xyyx
  xyxy
  
  
  Output
  
  
  NO
  YES
  NO
  YES
  YES
  YES
  NO
  NO
  NO
  YES
solution: #include <bits/stdc++.h>
  const unsigned int M = 1e9;
  using namespace std;
  int solve() {
    long long int t = 1;
    cin >> t;
    while (t--) {
      string s;
      cin >> s;
      int n = s.length() / 2;
      vector<char> vc;
      string st;
      string st1;
      for (int i = 0; i < n; i++) {
        vc.push_back(s[i]);
        st.push_back(s[i]);
      }
      for (int i = n; i < s.length(); i++) {
        st1.push_back(s[i]);
      }
      bool ch = true;
      if (st1 == st) {
        cout << "YES"
             << "\n";
      } else {
        cout << "NO"
             << "\n";
      }
    }
    return 0;
  }
  int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(0);
    clock_t z = clock();
    solve();
    cerr << "Run Time : " << ((double)(clock() - z) / CLOCKS_PER_SEC) << " ";
    return 0;
  }
  