Sudoku-solver

a sudoku solver using brute-force

How does it works?

The former algorithm:

function solve()

if no more cells to explore

  return true;

for each cell

  if this cell is empty

    try one choice i;
  
    if  i is a valid choice
  
      return solve()
  
    unmake the choice i;

return false;

Actually, it works, but too slow. I searched on the Internet, and then I realised that my algorithm could be improved: instead of this:

for each cell

  if this cell is empty
  ...

THIS (inspired by this one:https://www.tutorialspoint.com/sudoku-solver-in-cplusplus):

  At the first cell available (with function findEmpty() that will modify two variables, x and y, where is the first 0 in the grid)

  ...

Resulting algorithm:

function solve()

if no more cells to explore

  return true;

At the first 0 in the grid

  try one choice i;

  if  i is a valid choice

    return solve()

  unmake the choice i;

return false;