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>
  using namespace std;
  void _print(long long int x) { cerr << x << " "; }
  void _print(float x) { cerr << x << " "; }
  void _print(double x) { cerr << x << " "; }
  void _print(char x) { cerr << x << " "; }
  void _print(string x) { cerr << x << " "; }
  void _print(bool x) { cerr << x << " "; }
  template <class T, class V>
  void _print(pair<T, V> x) {
    cerr << "{";
    _print(x.first);
    cerr << ",";
    _print(x.second);
    cerr << "}";
  }
  template <class T>
  void _print(vector<T> x) {
    cerr << "[ ";
    for (T i : x) {
      _print(i);
      cerr << " ";
    }
    cerr << "]";
  }
  template <class T>
  void _print(set<T> x) {
    cerr << "[ ";
    for (T i : x) {
      _print(i);
      cerr << " ";
    }
    cerr << "]";
  }
  template <class T>
  void _print(multiset<T> x) {
    cerr << "[ ";
    for (T i : x) {
      _print(i);
      cerr << " ";
    }
    cerr << "]";
  }
  template <class T, class V>
  void _print(map<T, V> x) {
    cerr << "[ ";
    for (auto i : x) {
      _print(i);
      cerr << " ";
    }
    cerr << " ]";
  }
  void solve() {
    string s;
    cin >> s;
    long long int n = s.size();
    if (n % 2 == 1) {
      cout << "NO" << endl;
      return;
    }
    for (long long int i = 0; i <= (n / 2) - 1; i++) {
      if (s[i] != s[i + (n / 2)]) {
        cout << "NO" << endl;
        return;
      }
    }
    cout << "YES" << endl;
  }
  signed main() {
    ios_base ::sync_with_stdio(false);
    cin.tie(NULL);
    clock_t start, end;
    start = clock();
    long long int t;
    cin >> t;
    while (t--) {
      solve();
    }
    end = clock();
    double time_taken = double(end - start) / double(CLOCKS_PER_SEC);
    cerr << "Time taken by program is : " << fixed << time_taken
         << setprecision(5);
    cerr << " sec " << endl;
    return 0;
  }
  