#METHOD OF SOLVING SUDOKU PUZZLES HOW TO#
#METHOD OF SOLVING SUDOKU PUZZLES FULL#
#METHOD OF SOLVING SUDOKU PUZZLES CODE#

A binary search tree will allow an algorithm to go down one branch of choices, and then try a different brach of choices. When there is the option of two different numbers to solve a square, it is necessary to brach out into two different possibilities. This type of searching can be easily done with a computer using a binary search tree. You will then have to backtrack and try a different option. Choose one and keep solving until it becomes clear that the option you chose cannot be a solution. That means there are multiple paths you could choose and it is not obvious which path will lead to solving the puzzle.Īt that point it is necessary to try each option. Sometimes the board will reach a state where it seems that every unsolved square could potentially be multiple values. In the example below we can determine that the solution to the square highlighted in blue must be 6 since the number 6 does not occur in any other square in the yellow box.

If you keep finding the single candidates and then eliminating options from other squares, you may eventually reach the point where there are no more single candidates.Īt this point you can look for possible solutions to squares where the number is only in a single square in a box, row, or column. Now you know that the square highlighted in blue must be 7. Now that the two squares highlighted in yellow are known, that eliminates more possibilities from other squares. In the example below, the two yellow highlighted squares must contain 1 and 8 because all the other digits have been eliminated since they already appear in the column, row, or box of the square. That means to find a square that can only be one possible number.

#METHOD OF SOLVING SUDOKU PUZZLES FULL#

Most people will determine the possible number for one box at a time, instead of for the full grid.Īfter you eliminate numbers, you can look for single candidates. The possible numbers were determined by eliminating all digits that occur in the same column, row, or box. In the example below, the possible numbers for each square are noted in a smaller font. The second thing you should do is to look for a single candidate. The first thing you should do is to eliminate numbers from rows, columns, and boxes (3x3 subgrids). When solving a Sudoku puzzle, you should be constantly doing two things. In the image below from a Sudoku game, the number that should go in the blue highlighted square cannot be in any of the yellow squares corresponding to the column, row, and 3x3 box. The puzzles start with some numbers already on the grid and it's up to you to fill in the other numbers. The objective is to fill a 9x9 grid with digits (1-9) so that each column, row, and each of the nine 3x3 subgrids (also called boxes) all contain each of the digits from 1 to 9. This article is about the most popular type. Sudoku is a number-placement puzzle and there are a few different types.

#METHOD OF SOLVING SUDOKU PUZZLES CODE#

After reviewing Sudoku and some strategies, I will break down Norvig's code step-by-step so you can understand how it works. Norvig's solution is considered a classic and is often referred to when people develop their own code to play Sudoku. Peter Norvig developed an elegant program using Python to win sudoku using constraint propagation and search. Who needs thinking when you can let the computer think for you.

#METHOD OF SOLVING SUDOKU PUZZLES HOW TO#

But more importantly, you will learn how to use machine learning to easily solve every Sudoku puzzle. In this article, you will learn how to play and win Sudoku.

Now we have computers! (Ok, so most people still just use their minds.) When it first came out people had to actually solve the puzzles using only their minds. Sudoku (and its predecessors) has been played for over a hundred years.

Method of solving sudoku puzzles