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: //package Round762Div3;
  import java.util.*; 
  
  public class SquareString {
  
  	public static boolean checkSquare(String str) { //checks if string is a square
  		int len = str.length();
  		if(len % 2 == 1) {
  			return false; 
  		}
  		int half = len / 2; 
  		return str.substring(0, half).equals(str.substring(half, len)); 
  	}
  	
  	public static void main(String[] args) {
  		Scanner sc = new Scanner(System.in);
  		int t = Integer.parseInt(sc.nextLine()); //# of test cases 
  
  		for(int i = 0; i < t; i++) {
  			String str = sc.nextLine(); 
  			if(checkSquare(str)) {
  				System.out.println("YES"); 
  			} else {
  				System.out.println("NO"); 
  			}
  		}
  //		System.out.println(checkSquare("xyxy"));
  	}
  
  }
  