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.lang.*;
  import java.io.*;
   public class Solution{
      public static void main (String[] args) throws java.lang.Exception {
          int t = sc.nextInt();
          while(t-->0){
              String str = sc.nextLine();
              if(str.length()%2==0){
                  String s1 = str.substring(0, str.length()/2);
                  String s2 = str.substring(str.length()/2, str.length());
                  //System.out.println(s1+" "+s2);
                  if(s1.equals(s2)){
                      System.out.println("YES");
                  }else{
                      System.out.println("NO");
                  }
              }else{
                  System.out.println("NO");
              }
          }
      }
      // Fast Reader Class
      public static FastReader sc = new FastReader();
      public static BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));
      static class FastReader {
          BufferedReader br;
          StringTokenizer st;
          public FastReader() { br = new BufferedReader(new InputStreamReader(System.in));}
          String next() { while (st == null || !st.hasMoreElements()) { try { st = new StringTokenizer(br.readLine()); } catch (IOException e) { e.printStackTrace(); } }return st.nextToken(); }
          int nextInt() {
              return Integer.parseInt(next());
          }
          long nextLong() {
              return Long.parseLong(next());
          }
          double nextDouble() {
              return Double.parseDouble(next());
          }
          String nextLine() { String str = ""; try { str = br.readLine(); } catch (IOException e) { e.printStackTrace(); }return str; }
      }
  }
  //    int n = sc.nextInt(), p = sc.nextInt(), k = sc.nextInt();
  //            if(p%k<=(n-1)%k){
  //                    n--;
  //                    long ans = (p%k)*((n+k)/k)-((p%k-1)*(p%k))/(2*k);
  //                    System.out.println(ans);
  //                    ans+=(p-(p%k))/k+1;
  //                    System.out.println(ans);
  //                    }else{
  //                    long ans=0;
  //                    n--;
  //                    ans+=(n%k)*(n+k)/k;
  //                    ans+=(p%k-n%k-1)*(((n+k)/k)-1);
  //                    ans+=(p-(p%k))/k+1;
  //                    System.out.println(ans);
  //                    }