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: import java.util.*;
  import java.io.*;
  
  public class Main {
      public static boolean check(String str) {
          int len = str.length();
          if (len % 2 == 1) {
              return false;
          }
          for (int i = 0; i < len / 2; i++) {
              char c1 = str.charAt(i);
              char c2 = str.charAt((len / 2) + i);
              if (c1 != c2) {
                  return false;
              }
          }
          return true;
      }
  
      public static void main(String[] args) {
          Scanner scn = new Scanner(System.in);
          int t = scn.nextInt();
          while (t-- > 0) {
              String str = scn.next();
              if (check(str)) {
                  System.out.println("YES");
              } else {
                  System.out.println("NO");
              }
          }
          scn.close();
      }
  }