I'm trying to create a puzzle like the one below (image snagged from puzzlephil.com).
I know how to generate and solve sudoku 3x3 variation via C#, and I'm now trying to add a new variant, irregular sudoku, and I'm completely stuck.
The only explanation I've been able to find on the internet came from (http://www.clarity-media.co.uk/puzzleblog/creating-irregular-sudoku-puzzles) and states, "Writing a program to create them is not trivial, but also not too hard as long as you get your algorithm correct. One way is to start off with the orthodox 3x3 box regions. Then look for regions that are capable of exchanging a cell with a neighboring region - growing by one cell from the neighboring region whilst instantly losing a different cell to the neighbor."
This isn't descriptive enough. Can anyone explain how these irregular sudoku are created? I don't need/expect code, just a simple explanation of the process. This is my first post, I hope it's not too subjective. If so, please advise me how I can be more specific. Thanks!
EDIT: I'm making progress! I now start with a board containing rows such as: 1,2,3,4,5,6,7,8,9 - next row: 2,3,4,5,6,7,8,9,1 - etc. This gives me a starting board with 1-9 in each row and col but 3x3 regions have duplicates. I then randomly switch 2 rows and then 2 columns over and over creating a randomized grouping of numbers still conforming to the 1-9 in each row/col. That's where I am for now - I am going to attempt to "draw" the irregular shapes now using recursion and maybe a tree to prune paths that aren't valid. Still open to any tips but thank you to those replying as you've started me on a path.