Try writing it as a recursive solution - you will have a lot fewer lines. Define a function that takes the unsolved puzzle as a parameter, find one number that is a valid number for an empty cell and is the only valid number for it, update the puzzle, send it back to the original function.

Try writing it as a recursive solution - you will have a lot fewer lines. Define a function that takes the unsolved puzzle as a parameter, find one number that is a valid number for an empty cell and is the only valid number for it, update the puzzle, and then send it back to the original function.

Try writing it as a recursive solution - you will have a lot fewer lines. Define a function that takes the unsolved puzzle as a parameter, find one number that is a valid number for an empty and is the only valid number for it, update the puzzle, send it back.

Try writing it as a recursive solution - you will have a lot fewer lines. Define a function that takes the unsolved puzzle as a parameter, find one number that is a valid number for an empty cell and is the only valid number for it, update the puzzle, send it back to the original function.