(albeit a fraction of a second).Īpproach 2. I found a brute force approach solved all Sudoku games - but that came at a performance cost. To implement this approach we can use a simple loop and apply recursion (a function that calls itself with an altered or cut-down problem space) - the logic is only a few lines. With such an approach, it’s not uncommon to backtrack all the way to start several times. Should we exhaust all combinations in the current cell, we backtrack a loop, increment the previous cell value and begin again. At any point we encounter an impossible solution (a cell with no valid values), we try the next value, and then the next. We then move to the next empty cell, set that to 1 and check it’s valid. We can apply a backtracking algorithm by iterating over all the empty cells, beginning with the value 1 and checking it’s valid.
The first approach is applying brute force to the problem. I came to this challenge from two perspectives and in the end I used both techniques - using a combination was quicker for complex Sudoku puzzles.Īpproach 1. The output below is the starting position of the board for the game array pictured earlier. print_board(board) - a function that helps visualize the board/grid.
Solving sudoku full#
have we finished the puzzle? This function should check every row, every column, and every square has the full set of values 1–9.
However, in order to solve difficult levels and deal with them quickly, you need to use some tricks and learn advanced Sudoku techniques.
Therefore it’s not so difficult to cope with the solution if you are familiar with the basic rules. There are already many numbers filled in on the grid in the simple Sudoku puzzles. The game is over when the whole Sudoku grid is correctly filled with numbers.Each number in the 3×3 block, vertical column or horizontal row can be used only once.Each horizontal row can only contain numbers from 1 to 9.Each vertical column can only contain numbers from 1 to 9.Each 3×3 block can only contain numbers from 1 to 9.Its rules are quite simple, so even beginners can handle the simple levels. Sudoku is a popular logic puzzle with numbers. What is Sudoku and what are the rules of this game?