The New Sudoku Players' Forum

[Richard S]

Here a double killer.

- Both grids have exactly the same solution.
- Instead of 1 to 9 the digits 0,0,1 to 7 have to be placed in every row, column, nonet and both diagonals.
- Only the zero may appear twice in a cage.

Enjoy, Richard

[Scott H]

Very challenging puzzle! Delightful chains of difficult constrained reasoning from start to end.
Since it's a double killer, is it supposed to have two solutions? That's what I found.

[Richard S]

Both grids should have exactly the same solution, which is a unique solution if you combine the givens in both grids...

[Richard S]

Thanks for your response Scott!

While reading you had found multiple solutions I thought: Impossible!

But after receiving your PM with two solutions I looked a bit better and found out where I had made my 'thought'-error:

This puzzle was formed around the 28-cage in the middle. In sudokus without repeating numbers is the rule for such a cage: R3C5 + R7C5 = R56C6.

I made the mistake to think the same in this puzzle! And when R7C5 is also in R56C6 and these are both in the same cage, R7C5 and one of the numbers in R56C6 must be a zero. This is wrong. R3C7 has to be a zero, in R56C6 this is not per definition the case.

What I am surprised about is that this puzzle is in a few forums for more than a week now, and no one else figured out this multiple solutions. I guess everybody made the same mistake as I did.

So: thanks for your post!
I learned something important.

Richard