public static String gridChallenge(List<String> grid) {
// Write your code here
    List<String> squareMatrixList = new ArrayList<>();
    //row sorting
    for(int i =0; i < grid.size(); i ++){
       char[] rowsorted = grid.get(i).toCharArray();
       Arrays.sort(rowsorted);
       squareMatrixList.add(String.valueOf(rowsorted));
    }
    System.out.println(squareMatrixList.toString());
    int size = squareMatrixList.size();
    int strLength = squareMatrixList.get(0).length();
    for(int col =0; col < strLength; col++){
        for(int row = 0; row < size -1; row++){
            String str1 = squareMatrixList.get(row);
            String str2 = squareMatrixList.get(row +1);
            if(str1.charAt(col) > str2.charAt(col)){
                return "NO";
            }
        }
    }
    return "YES";
}

Python solution

def gridChallenge(grid):
    sorted_grid = ["".join(sorted(row)) for row in grid]
    num_cols = len(sorted_grid[0])
    num_rows = len(sorted_grid)
    
    for col_idx in range(num_cols):
        columns = []
        for row_idx in range(num_rows):
            columns.append(sorted_grid[row_idx][col_idx])
       
        if columns != sorted(columns):
            return "NO"
    return "YES"

Test case contains non-square grid which violates task description

I love this platform. OnlyTestcase 10 fails. It has 100 inputs, with HUGE size. I try to copy the input into custom output to try to see the difference in my answer. Error, input size too big.

Okay thank you. ><

Somehow this grid is not square, even though they say so...