Sudoku solver in Java, using backtracking and recursion

Question

I am programming a Sudoku solver in Java for a 9x9 grid.

I have methods for:

• printing the grid

• initializing the board with given val

Answer 1

i suggest passing both the current row and column to the recursive method then find all allowed numbers for THAT cell, for each allowed number recursivly call the method for the next column (or next row if at last column) and undo the move if it leads to a dead track

public boolean fillCell(int r, int c) {
    if last row and last cell {
        //report success
        return true
    }
    for i 1 to 9 {
        if can place i on r, c {
            board[r][c] = i
            if !fillCell(next empty row, next empty column) { //DONT change r or c here or you will not be able to undo the move
                board[r][c] = 0
            }
            /*
            else {
                return true; //returning true here will make it stop after 1 solution is found, doing nothing will keep looking for other solutions also
            }
            */

        }
    }
    return false        
}