23 replies to this topic

[LuaEclipser]

my brain hurts just thinking on how to do it



there have been many attempts, and many fails. who will succeed?




CHALLENGE.ACCEPTED

[Kryptanyte]

LuaEclipser, I think I may have an idea for an algorithm for leaving the numbers on the screen, so its an actual playable sudoku I'll try and come up with it and send it to you if you are able to do the rest?

[Zanoab]

I think I'll take on this challenge as well. Funny thing is that generating a random valid solution is just as difficult as turning a solution into a puzzle without multiple solutions.

While writing my board object initialization code, I realized you can't just up and put random numbers. I did a quick test on paper and if you don't restrict your number generation after generating the first few numbers, it is possible for the board to end up with "bubbles" and instantly becomes an invalid solution.

What I mean:

Spoiler

Here is a quick 2d example (squares and rows):
1 2 3 | 4 5 6 | 7 8 9

Let's say you then generate the first 3 numbers of the next row:
5 6 7 |

It is now possible to trap your random number generator if you don't check the available placements:
1 2 3 | 4 5 6 | 7 8 9
5 6 7 | 1 2 3 | 4

In order to prevent this, you would have to analyze the available number placements:
4 can't be placed in Square 2 so it must be placed in Square 3
8 and 9 can't be placed in Square 3 so it must be placed in Square 2
1 2 3 | 4 5 6 | 7 8 9 (0's will be used as blanks)
5 6 7 | 8 9 0 | 4 0 0

Now let's do Row 3:
1 2 3 | 4 5 6 | 7 8 9
5 6 7 | 8 9 0 | 4 0 0
4 8 9 | 7 0 0 | 5 6 0

Now we can fill the remaining spots with 1, 2, and 3 and the board is 33% filled.

On the bright side, the fun doesn't stop there (sarcasm). That example was only a 2d example (rows and squares) when the complete board is 3d (rows, columns, and squares). Once you start adding all the details to reduce the chances of generating an invalid solution...

td;dr version: we are literally writing a sudoku solver that supports blank boards (strategically and/or bruteforce).

[SuicidalSTDz]

Glad to see people taking an interest in this.