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;
  inline void debug(vector<long long>& arr) {
    cout << "arr: [";
    for (auto it : arr) {
      cout << it << ",";
    }
    cout << "]";
    cout << '\n';
  }
  inline void debug(long long x) { cout << x << '\n'; }
  inline void debug(long long arr[], long long n) {
    cout << "arr: [";
    for (long long i = 0; i < n; i++) {
      cout << arr[i] << ",";
    }
    cout << "]";
    cout << '\n';
  }
  const long long N = 1e5 + 5;
  int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    ;
    long long t;
    cin >> t;
    while (t--) {
      string str;
      cin >> str;
      long long n = str.length();
      if (str.length() % 2 == 1) {
        cout << "NO" << '\n';
      } else {
        string s, s1;
        long long i = 0;
        for (i; i < n / 2; i++) {
          s.push_back(str[i]);
        }
        for (i; i < n; i++) {
          s1.push_back(str[i]);
        }
        if (s == s1) {
          cout << "YES" << '\n';
        } else {
          cout << "NO" << '\n';
        }
      }
    }
    return 0;
  }
  