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 cf762{
      public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          cf762 ob = new cf762();
          int n = sc.nextInt();
          for(int i = 0; i < n; i++) {
              System.out.println(square(sc.next()));
          }
      }
  
      static String rev(String s) {
          String reverse = "";
          for(int i = s.length()-1; i >= 0; i--) {
              reverse += s.charAt(i);
          }
          return(reverse);
      }
  
      static String square(String s) {
          if(s.length() % 2 != 0) {
              return("NO");
          }
          else {
             int spl = s.length()/2;
             int z = 0, x = s.length()-1;
             String str1 = "", str2 = "";
             while(z <= spl && x >= spl) {
                 str1 += s.charAt(z);
                 str2 += s.charAt(x);
                 z++;
                 x--;
             }
             //System.out.println("Str1 = " + str1);
             //System.out.println("Str2 = " + rev(str2));
             str2 = rev(str2);
             if(str1.equals(str2)) {
                 return("YES");
             }
             else
                 return("NO");
          }
      }
  }
  