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Learn to play Sudoku on your cell phone, Or play at any skill level...

Warning: This may be difficulty to follow, If you don't know how to play Sudoku you should start in the easy section first.

Here is an example of an Grandmaster level puzzle being solved using Sudoku Tutor's in game solver. If you feel you are good at Sudoku already this example will show that there is something to be learned, even by a Sudoku Enthusiast.

The squares highlighted in yellow are squares that can be automatically filled because there is only one number possible for that square.

The Green Squares Represent that the number in yellow is that number because that number would not be possible in any of the green squares.



Once the solver reaches a point where there are no automatic squares to be filled in it makes a guess from  a square that has the least possible values. This is denoted in purple. Then the Solver continues to try for a solution as if that guess was a valid solution value.



If the solver reaches a point where the puzzle cannot be solved because there is a square with no possible value that square gets denoted with a red X.



Solver then goes back to the most recent guess. In this case square [1,1] marks that 2 is not possible and moves to the next possible value. In this case the only value left is 3. So that gets entered as a correct value.

(This will almost always happen because the solver guesses using a square with the least possible values, so as long as there was at least one square on the board with only two possible values that would have been the square Solver used.)



When filling in the puzzle again Solver may still need to make some guesses. And may again have made an incorrect guess.



In which case it will go back to the most recent guess that it made. In his case [3,2] which had a six now is assumed to be wrong. And the solver will continue as if 7 were the correct value. (Even though later we will find out it is not 7 but 6, it is actually the 2 that is wrong, This Is why this puzzle is ranked Grandmaster)



Continuing through the puzzle leads to yet another dead end.



And solver must backtrack to square [7,2] to make the value 8 instead of the 6 that it previously guessed. and then continue towards a valid solution.



This time almost right away we see that this still does not lead to a valid solution. But there is only one guess made on the whole board at this point. So Solver goes back to that guess marks it as wrong and continues on. (Yes all that work was only useful to find out that 2 was wrong in square [2,1]). Solver changes to 8, the next possible value for the square, and continues on towards a solution. Since there are no guesses on the board at this point and 8 is the only other value possible in [2,1] solver knows 8 is correct.



Still we arrive at a problem and must backtrack again to square [7,1]. But the good news is that this determination means clear sailing for the rest of the puzzle. Which at this point would be classified as easy. Just follow the auto fill ins to a solution.




Note here that 6 in square [3,1] is purple because it had been a guess and was never proven wrong. So you can see that the guess turned out to be correct. This is puzzle number 4 in the game, there are 20 built in Grandmaster level puzzles to try either on your own or with the solver. And the game also has the ability to let you enter your own puzzles too.