grid-challenge.java

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
       
        for(int i=0; i<k; i++){
             int n = in.nextInt();
             char[][] arr = new char[n][n];
             for(int j=0; j<n; j++){
                 String str = in.next();
                 arr[j] = str.toCharArray();
             }
             checkSort(arr);
        }
    }
    
    public static void checkSort(char[][] arr){
        //sort each row
        for(int i=0; i<arr.length; i++){
            Arrays.sort(arr[i]);
        }
        //check whether for each column, numbers are in increasing order
        for(int j=0; j<arr[0].length; j++){
            for(int i=0; i<arr.length-1; i++){
                if(arr[i][j]>arr[i+1][j]){
                    System.out.println("NO");
                    return;
                }
            }
        }
        System.out.println("YES");
    }
    
    
}