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;
  const long long N = 1e5 + 5;
  const long long mod = 998244353;
  const long long inf = 1e18 + 5;
  template <typename T>
  ostream& operator<<(ostream& os, vector<T> v) {
    for (auto& i : v) os << i << ' ';
    return os;
  }
  template <typename T>
  istream& operator>>(istream& is, vector<T>& v) {
    for (auto& i : v) is >> i;
    return is;
  }
  template <typename T, typename U>
  istream& operator>>(istream& is, pair<T, U>& p) {
    is >> p.first >> p.second;
    return is;
  }
  template <typename T, typename U>
  ostream& operator<<(ostream& os, pair<T, U> p) {
    os << p.first << ' ' << p.second << '\n';
    return os;
  }
  void read() {
    freopen("cowtip.in", "r", stdin);
    freopen("cowtip.out", "w", stdout);
  }
  void solve() {
    string s;
    cin >> s;
    long long n = s.size();
    if (n & 1) {
      cout << "NO";
      return;
    } else {
      for (int i = 0; i < n / 2; i++) {
        if (s[i] != s[i + n / 2]) {
          cout << "NO";
          return;
        }
      }
      cout << "YES";
    }
  }
  int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int32_t T = 1;
    cin >> T;
    while (T--) {
      solve();
      cout << '\n';
    }
    cerr << "\nTime elapsed:" << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
  }
  