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 squarestring {
  
  	public static void main(String [] args)
  	{
  		Scanner in =new Scanner(System.in);
  		int n=in.nextInt();
  		String [] str=new String[n];
  		in.nextLine();
  		int i,j,k,m,z=1;
  		for(i=0;i<n;i++)
  		{
  			str[i]=in.nextLine();
  		}
  		
  		for(i=0;i<n;i++)
  		{
  			
  			//System.out.println(i);
  			z=1;
  			k=str[i].length();
  		//	System.out.println(k);
  			if(k%2!=0)
  			{
  			    z=10;
  				System.out.println("NO");
  			
  			}
  		
  			for(j=0;j<k/2;j++)
  			{	
  				if(z==10)
  				{
  					break;
  				}
  				else
  				{
  					z=0;
  				    m=k/2;
  					if(str[i].charAt(j)==str[i].charAt(m+j))
  					{
  						z=3;
  						
  						//System.out.println(m);
  						
  					}
  					else
  					{
  						System.out.println("NO");
  						break;
  					}
  					
  				// m++;
  			  }
  			
  		}
  			if(z==3)
  				System.out.println("YES");
  			    
  		}
  		
  		
  	}
  }