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 would check each cell and go back a recursion step if no solution can be found.

In more detail: Go to next cell, if value x == 0, check if x+1 would be valid, if true, go to next cell by calling the method recursively with the next possible cell. If the number is not valid check x+2 etc. if no number is valid return false and repeat the x+1 step in the previous call. If you hit a cell with a number inside, do not call the recursion but directly go to the next, thus you need not to flag any pre entered cells.

Pseudo code:

fillcell cell
 while cell is not 0
  cell = next cell
 while cell value < 10
  increase cell value by one
  if cell is valid 
    if fillcell next cell is true
      return true
return false

Not sure if this correct but it should show the idea.