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.io.*;
  import java.math.BigInteger;
  import java.util.*;
  import static java.lang.Math.PI;
  import static java.lang.System.in;
  import static java.lang.System.out;
  import static java.lang.System.err;
  
  public class A {    
      public static void main(String[] args) throws Exception {   
          Foster sc = new Foster();
          PrintWriter p = new PrintWriter(out);
  
         /*
          * Is that extra condition needed
          * Check overflow in pow function or in general
          * Check indices of read array functions
          * Think of an easier solution because the problems you solve are always easy
          * Check the iterator of loop
          */   
  
          int t = sc.nextInt();
          while(t--!=0) {
              char a[] = sc.next().toCharArray();
              if(a.length%2!=0) {
                  p.println("NO");
                  continue;
              }
              int mid = a.length/2;
              boolean poss = true;
              for(int i = 0; i < mid; i++) {
                  if(a[i] != a[mid+i])    poss = false;
              }
              p.println(poss ? "YES" : "NO");
          }
          p.close();
      }
      
      static long[] sort(long a[]) {
          ArrayList<Long> arr = new ArrayList<>();
          for(long i : a) {
              arr.add(i);
          }
          Collections.sort(arr);
          for(int i = 0; i < arr.size(); i++) {
              a[i] = arr.get(i);
          }
          return a;
      }
      static int[] sort(int a[]) {
          ArrayList<Integer> arr = new ArrayList<>();
          for(int i : a){
              arr.add(i);
          }
          Collections.sort(arr);
          // Collections.reverse(arr);
          for(int i = 0; i < arr.size(); i++){
              a[i] = arr.get(i);
          }
          return a;
      }   
  
      static class Foster {
          BufferedReader br = new BufferedReader(new InputStreamReader(in));
          StringTokenizer st = new StringTokenizer("");
          String next() {
              while (!st.hasMoreTokens())
                  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());
          }
          int[] intArray(int n) {
              int arr[] = new int[n];
              for(int i = 0; i < n; i++) {
                  arr[i] = nextInt();
              }
              return arr;
          }
          long[] longArray(int n) {
              long arr[] = new long[n];
              for(int i = 0; i < n; i++) {
                  arr[i] = nextLong();
              }
              return arr;
          }
          static long pow(long... a) {
              long mod = Long.MAX_VALUE;
              if(a.length == 3)   mod = a[2];
              long res = 1;
              while(a[1] > 0) {
                  if((a[1] & 1) == 1)
                      res = (res * a[0]) % mod;
                  a[1] /= 2;
                  a[0] = (a[0] * a[0]) % mod;
              }
              return res;
          }
          static long gcd(long a, long b) {
              if (b == 0)
                  return a;
              return gcd(b, a % b);
          }
      }
  }