# Sudoku Help

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

## Instructions

**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

- it must be a printable string
- it should be backward-compatible
- it must use the numbers 1 to 9 to represent a set number in a number-cell
- it must be parse able with a reasonably lax sudoku parser taking a 81 character input

- it should be easy to implement
- it should be human read- and understandable

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 http://heuscher.ch/SudokuHelp

Feedback is very welcome! My email address is sTv@heuscher.ch

Question posted in

- http://www.setbb.com/phpbb/viewtopic.php?t=1337&mforum=sudoku
- http://www.sudoku.com/forums/viewtopic.php?t=5269 second page

## Tips

### Generated Sudokus

Sudokus: 0 . Background-generated sudokus:Diese Seite in Deutsch.