SudokuSolver Forum

This is the puzzlemadness.co.uk Daily Hard Killer Sudoku Puzzle dated 30 July 2023. This puzzle does not seem particularly difficult, but after a few seemingly obvious/simple moves, the puzzle winds up as being unsolvable.

Here are the steps I took:

1. clean up due to N8cage3
2. clean up due to N6cage17
3. clean up N6cage 9
4. 45 rule c6
5. 45 rule c5
6. N8cage24 - must have an 8, clean up N8 and col 6
7. cleanup N2cage12 and N5cage11
8. 45 rule N3
9. clean up col 6 (remove 2)
10. cleanup N5cage11
11. col 6, only 9 in N2cage12 - remove [57]
12. clean up due to N2cage12
13. 45 rule c5
14. clean up N8cage24
15. 45 rule c5
16. clean up N2cage21
17. 45 rule c5
18. clean up N8cage24

The problem is that at this point, only 6 in col 6 is N5cage11, so its solution becomes [56]. But then, N8cage24 cannot be solved. What on earth did I do wrong?

Hi groston
Hard to see what you are doing wrong without more detail. Some suggestions....
-can you include a snip of the original puzzle picture when you ask about a puzzle? I couldn't work out all the cages on yours without going to the puzzle page.
-you could include more detail in your steps

eg 4. 45 rule c6: 2 outies r3c7 + r9c5 = 9 = [18/27/45]

It looks like step 4 could be where you've made the mistake. Your two placements don't add to 9. Here's the "45" I used



It gets 0.90

Cheers
Ed

Ed - Thank you. You found my moronically stupid mistake. Sigh - when I did step 4, I forgot that r3c7 was a part of N3cage7 - I really messed up. Thanks.

I was about to have a look at this but Ed got there first.

Your diagram is indeed hard to follow. Colouring nonets doesn't help, it would be easier to follow without that colouring and it's unnecessary since the thicker lines make the nonets clear. Coloured cages are better still, although Ed's diagram is clear with only coloured cages to highlight a step. I colour my cages manually using Excel worksheets, maybe your program doesn't allow for cages to be coloured; programming colouring of cages may not be easy.

Also when asking where you've gone wrong it would help if some of your steps gave a bit more detail, for example step 4 45 rule c6 did what? Similarly for the other 45 steps. So a bit more detail please if you need to ask us for help again.

As you've said, r3c7 is part of the 7(3) cage, 45rule c789 r3c7 = 4 so r34c6 = 3, r12c6 = 12, r56c6 = 11 -> r789c6 = 19, r9c5 = 5

Similarly 45 rule c123 r7c3 = 1 so r67c4 = 12, r45c4 = 12, r89c4 = 3 -> r123c4 = 18, r1c5 = 3

Cheers,

Andrew