Sudoku Solver for AndroidCheck out the App features. SudokuWiki.org Strategies for Popular Number Puzzles
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Window numbers Referred to in strategy results are:

 1 2 3 1 2 3 1 2 3 4 5 6 4 5 6 4 5 6 7 8 9 7 8 9 7 8 9 1 2 3 1 2 3 1 2 3 4 5 6 4 5 6 4 5 6 7 8 9 7 8 9 7 8 9 1 2 3 1 2 3 1 2 3 4 5 6 4 5 6 4 5 6 7 8 9 7 8 9 7 8 9
 Colour Sudoku Solver Please report any bugs and feedback welcome
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 2.12 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.

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, E5 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.

I have created enough test stock to grade this type of puzzle. However the Solution Count program also needs working on and I hope to make it available in the future.

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.

Colour Sudoku solver created 19th May 2011

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 17-Jul-2014.