Reading an input file n x n grid and reading empty space

I am trying to read an input file for something for an n x n fifteen sliding puzzle solver. The actual solving is not important right now because I can't even get through the input file reading part.

A number of board input files will be sent in and they look like this:

3
5  1  2
8     3
4  6  7

the top number is n (n x n grid). The input files cannot be changed so I can't make my life easier by representing the space with a 0 and then reading normally. I want to be able to read it into the code as a 2d array like so:

5 1 2
8 0 3
4 6 7

(0 representing the empty space at (1, 1) in the code)

The exact number of spaces between the numbers are also kind of weird in the input files because sometimes it's 2 spaces and sometimes it's 1 space (e.g. here's another larger input file):

9
38 51 15 17 11 27  8 36  7
19 40 28 10 14  4 77 26  9
43  2  5 18 71 22 20 32 13
37 34 76  6 48 25 35 44 53
1 56 65 39 70 24 62 79 42
30 74 68    58 55 45 60 33
67 29 75  3 41 59 73 63 80
47 12 31 49 50 61 57 72 16
66 23 64 21 78 54 69 52 46

I tried this:

File input = new File(args[0]);
Scanner scanner = new Scanner(input);

int n = scanner.nextInt();
scanner.nextLine();
int[][] board = new int[n][n];
int emptyRow = -1;
int emptyCol = -1;

for (int i = 0; i < n; i++) {
	for (int j = 0; j < n; j++) {
		if (scanner.hasNextInt()) {
			board[i][j] = scanner.nextInt();
		} else {
			// Empty space
			board[i][j] = 0;
			emptyRow = i;
			emptyCol = j;
		}
	}
}

It outputs this for the example 3x3 above:

5 1 2 
8 3 4
6 7 0

So, it doesn't even know at what position the empty space is; I'm not sure what to do here.

If fixed number (spaceNum) spaces split each row of the input data, you can read each line n times and divide each line by the spaceNum spaces.

Here is a sample:

for (int i = 0; i < n; i++) {
    int[] row = Arrays.stream(scanner.nextLine().split(" {"+spaceNum+"}")).mapToInt(s -> {
        try{
            return Integer.parseInt(s.trim());
        }catch (NumberFormatException e){
            return 0;
        }
    }).toArray();

    board[i] = row;
}

This should work for your examples. The idea is to process each line separately, find all numbers in it.

If there are not enough numbers, then a line contains an empty cell. In this case we should find the location of it and skip it.

public static int[][] main(String[] args) throws FileNotFoundException {
    File input = new File(args[0]);
    Scanner scanner = new Scanner(input);

    int n = scanner.nextInt();
    scanner.nextLine();
    int[][] board = new int[n][n];
    int currentRow = 0;

    while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        var digits = Arrays.stream(line.split(" "))
                .filter(d -> !Objects.equals(d, ""))
                .map(Integer::parseInt)
                .collect(Collectors.toList());

        int emptyCellIndex = -1;
        // found empty cell
        if (digits.size() != n) {
            emptyCellIndex = (line.indexOf("   ") + 2) / 3;
        }
        int iter = 0;
        for (int i = 0; i < n; i++) {
            if (i == emptyCellIndex) {
                continue;
            }
            board[currentRow][i] = digits.get(iter);
            iter++;
        }
        currentRow++;
    }
    return board;
}