dailysudoku.com

[immpy]

Hello all, enjoy the puzzle.

[dongrave]

Thanks for the puzzle immp! I couldn't find a single step solution so I settled for 2 (very convoluted) chains.

After basics:

[immpy]

Yes, I can understand that dongrave. This one was closer to an "extreme" or "unfair" level. I needed many steps to whittle it down, including chains. Maybe a rating of +++ would have been more accurate.

cheers...immp

[glesco]

I used a candidate colouring method that keys off bivalued cells though the solution is similar to dongraves. The steps I took:

- The 9s in c37 eliminate 9 in r8c9 in a finned x-wing thus creating a 48 bivalued cell in r8c9.
- Then I starting colouring candidates in Green or Blue ("G" or "B") if there is a strong link. Picked r9c1 to start making 6B & 8G. That makes in r7c1, 6G as it is a strong link in box 7.
- In r9c9 is 6G & 8B. In r8c9 the 8 is G as it is a strong in box 9 and thus the 4 becomes B.
- Now I looked for bivalued cells that see a colour with the same #, like the 24 in r2c9 that sees a 4B in r8c9. If B is the solution the 2 would be B.
- That 2B sees the 28 cell in r3c3 thus that 8 would B.
- We can eliminate 8 from r8c3 it sees a 8G in r8c9 as well as the 8B from above. This highlights an XY-wing
- That elimination creates a 29 bivalued cell in r8c3.
- Continuing on down c3 with the what if B is the solution scenario, in r6c3 the 9 becomes a B so in r8c3, the 2 becomes a B.
- But the 6 in r7c1 is G so r7c1 can not be 2!
- Continuing in box 7 with the same B is the solution scenario, in r8c3 the 2 is B so the 4 in r7c2 is B.
- But the 6 in r7c1 is G so r7c1 can not be 4!

Hope this is somewhat clear.

Eliminating 2&4 from r7c1 seems to be the key in this puzzle.

I used different approach from a lot of replies in this forum, let me know what you think!

[immpy]

Nice going glesco, that works.

cheers...immp