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Sudoku Help

This page helps you solve any sudoku. The rules of the game are documented in Wikipedia.


Start game: Easy, hard, very hard or random.

Click on numbers: All possibilities are updated. (Button "Undo" undoes an incorrect entry)
Click on numbers + press the Delete-Button: Delete the clicked number.

Representing the Sudoku during its Solution Process

There seems to be a common understanding of how to represent a sudoku as a string for sharing sudokus. It's a string of 81 numbers, each representing the number set or "0" if no number was set in the in a number-cell. An example: 000012034000056078000000000000000000410000085290000067000000000120039000980047000.

The problem I came around was: How do you encode a sudoku with ruled-out numbers? The player has ruled out some candidates and deleted them from the possibilities in the cell.

The representation has to be a string that can be shared via web and email and that can easily be copy-pasted. This means that

In the solution I propose, one sudoku is represented by two strings.

The first string is comprised of 81 numbers and "-" characters, each representing the number set, "0" if no number was set or "-" characters if a number was deleted in a number-cell. The "-" character indicates that one or more numbers have been deleted manually.

The second string is composed X instances of groups of one "-" character and numbers from 1 to 9. X equals the number of "-" characters in the first string. The index of the group references the "-" in the first string where the numbers in the groups represent deleted numbers, e.g., the 4th group "-378" indicates that the numbers 3, 7, and 8 were deleted from the number-cell holding the 4th "-" in the first string.

An example: 00001203400005607800-000000000-00000410000085290000067000000000120039000980047000 -34-189 (the group "-34" indicates that the numbers 3 and 4 have been deleted in that number-cell with the first "-" and the group "-189" indicates that the numbers 1, 8, and 9 have been deleted in that number-cell with the second "-").

If you are interested in trying it, go to

Feedback is very welcome! My email address is

Question posted in


Generated Sudokus

Sudokus: 0 . Background-generated sudokus:

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