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 Colour Sudoku Solver Please report any bugs. Tested in IE, Firefox, Safari and Chrome. Feedback: Form and User Comments/Questions Here
Candidates can be Edited or Highlighted / Shown
Enter numbers here:
 1 2 3 4 5 6 7 8 9
 Auto Tab Auto Clear
Clues+Solved: 0/81
 Pick an example here Easy 1 Easy 2 Easy 3 Moderate 1 Moderate 2 Moderate 3 Tough 1 Tough 2 Tough 3 Quite Hard 1 Quite Hard 2 Quite Hard 3 Extremely Hard 1 Extremely Hard 2 Extremely Hard 3

Puzzle Rules

Enter the numbers 1 to 9 uniquely in every row, column, box and colour. Each colour is in the same position relative to each 3x3 box.

Pick an example from the list and use Take Step to click through the steps of the solver so see how each puzzle solves.
 A B C D E F G H J
Version 2.06
See Strategy Overview documentation

Coordinate system: Letter/Number rYcX

 1 2 3 4 5 6 7 8 9
 Check for Solved Cells Show Possibles 1: Singles in Row/Column 2: Singles in Colour/Box 3: Naked Pairs/Triples 4: Hidden Pairs/Triples 5: Naked Quads 6: Pointing Pairs 7: Box/Line Reduction Tough Strategies 8: X-Wing 9: Simple Colouring 10: Y-Wing 11: Swordfish 12: XYZ Wing Diabolical Strategies 13: X-Cycles 14: XY-Chain 15: 3D Medusa 16: Jellyfish 17: WXYZ Wing 18: Aligned Pair Exclusion Extreme Strategies 19: Grouped X-Cycles 20: Finned X-Wing 21: Finned Swordfish 22: Altern. Inference Chains 23: Sue-de-Coq 24: Digit Forcing Chains 25: Nishio Forcing Chains 26: Cell Forcing Chains 27: Unit Forcing Chains 28: Almost Locked Sets 29: Death Blossom 30: Pattern Overlay Method 31: Quad Forcing Chains "Trial and Error" 32: Bowman's Bingo

Please report any bugs - Thanks.

If you are getting errors please
to retrieve the latest script files.

## The Colour Sudoku Solver

Colour Sudoku is the puzzle as normal Sudoku with an extra constraint. In a similar way to the rows, columns an boxes, the colours must also be uniquely 1 to 9. Each colour is in the same position in each 3x3 box, as you will notice with the central white cell, for example. All Sudoku strategies continue to apply - except the ones that rely on the deadly pattern used by Uniqueness strategies. Almost

The extra constraint does not add any extra complexity in the rows and columns - since a uniqueness constraint already exists, but it does effect cells diagonally. For example, B2, C5 and H8 are now connected and a conjugate pair may exist on those cells. So, like Sudoku X, the solver needs to be aware of all the new diagonal opportunities that are now possible.

Interestingly, this constraint forces the Sudoku puzzle to be 'perfect', that is, every number appears in a different position relative to each 3x3 box.

Note also that I have not completed the grading of this type of puzzle so I cannot offer a grading option in this version. The Solution Count program also needs updating to this will be available after the next update.

All feedback, comments, arguments, bug reports and strategy ideas are welcome. There is a new FEEDBACK form with a column displaying comments and questions. Many thanks to all the people who have done so and helped improve this solver.

Original version 1.01 28th May 2005

New in version 1.99 (April 9th 2014)
Unchecked strategies are now saved in a cookie.

On the small board for number entry I have added an option that automatically clears off candidates as numbers are added. Also, changes to the small board are automatically saved.

I have redesigned the way cookies are stored and puzzles loaded. You still have a manual save and reload but the solver now automatically saves the board every time it changes. Should you loose the page it will restore the puzzle you were working on. Cookies also retain the difference between clues and solved cells as well.

I sped up the "Take Step" process by skipping failed strategies and going straight to the first successful one. This applies to the basic strategies which are client-side. If you get "script taking too long" messages from your browser, let me know. It's a bit risky for slower machines and I'd like to find out if this works for everyone.

Full version history here

## Solver help

Use the "Import a Sudoku" button or type in a Sudoku puzzle in the small board.
You can also pick examples from the list above. Click on Take Step to step through the solution. Unknown squares are filled with 'candidates' - possible solutions.
Any cells that are reduced to one possible candidate are solved.

You can use the [<<] button to step back one go. Toggling between Take Step and [<<] helps you see the changes.

Pressing "Enter" on the keyboard after clicking on Take Step is a quick way to activate "Take Step". Details of any solutions will be written out in the text box below the big board. Strategies are ordered by complexity. Any strategy that is successful returns the step-through to the start.

Click on the board to highlight sets of numbers. You can edit the Sudoku at any time - entering solutions in the small board or editing candidates. (Toggle between highlighting and editing using the radio buttons at the top.)

Solver created on 28-May-2005.