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 Main
  {
  	public static void main(String[] args) {
          int t,flag;
          Scanner s =new Scanner(System.in);
          int flag2=0;
          t=s.nextInt();
          s.nextLine();
          for(int i=0;i<t;i++){
          HashMap<Character,Integer> map=new HashMap<Character,Integer>();
              flag=1;
              String str=s.nextLine();
              int n=str.length()/2;
              for(int j=0;j<str.length();j++){
                  map.put(str.charAt(j),map.getOrDefault(str.charAt(j),0)+1);
              }
           
           for(int val : map.values()){
               if(val%2 !=0){
               System.out.println("NO");
              flag=0;
              break;
               }
           }
           
           if(flag==1){
               for(int k=0;k<n-1;k++)
               {
                   if(str.charAt(k) != str.charAt(n + k)){
                       flag=0;
                       break;
                   }
               }
               if(flag==1)
               System.out.println("YES");
               else
               System.out.println("NO");
           }
          }
  	}
  }