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.*;
  public class square_string
  {
      static int arr[]=new int[26];
      public static void output(String str)
      {
          int length=str.length();
          if((length%2)!=0)
          {
              System.out.println("NO");
          }
          else
          {
              String nstr1,nstr2;
              nstr1=str.substring(0,(length/2));
              nstr2=str.substring((length/2),length);
              if(nstr1.equals(nstr2))
              {
                  System.out.println("YES");
              }
              else
              {
                  System.out.println("NO");
              }
          }
      }
      public static void main(String args[])
      {
          Scanner in=new Scanner(System.in);
          int t,i;
          String str;
          t=in.nextInt();
          for(i=0; i<t; i++)
          {
              str=in.next();
              output(str);
          }
      }
  }