Re:There are only twelve 4x4 sudokus (and a cool trick for f...
by probably_wrong on Tuesday September 15, 2026 @08:24AM
(#49711485)
I was wondering this myself so I wrote a script that shows that there are duplicated puzzles if you count a rotated Sudoku as being equivalent. Here's one example:
Puzzle 2 is
1234
3412
2341
4123
If you rotate it counterclockwise you have
4213
3142
2431
1324
And if you normalize it, replacing the first row with "1234" (brilliant idea from the post), you get
1234
4312
2143
3421
Which is listed as puzzle 7. A quick check gives me that puzzles 1, 2, 3, 5, 11 and 12 would be unique under rotation, but I wrote that check in five minutes so there must be bugs somewhere. Also, I performed no check for mirror symmetry whatsoever (update: I did a quick one, same result).
I don't want to miss my chance to say that the post is brilliant and that it convinced me to leave what I was doing to check for rotations. I was nerd sniped in the best way and I take my hat off for the OP.
Puzzle 2 is
If you rotate it counterclockwise you have And if you normalize it, replacing the first row with "1234" (brilliant idea from the post), you get Which is listed as puzzle 7. A quick check gives me that puzzles 1, 2, 3, 5, 11 and 12 would be unique under rotation, but I wrote that check in five minutes so there must be bugs somewhere. Also, I performed no check for mirror symmetry whatsoever (update: I did a quick one, same result).I don't want to miss my chance to say that the post is brilliant and that it convinced me to leave what I was doing to check for rotations. I was nerd sniped in the best way and I take my hat off for the OP.