Puzzle Description Suppressed:Click below to view spoilers

#1: derby (Derby) on Jul 12, 2023 [SPOILER]

Comment Suppressed:Click below to view spoilers

Initial line & color logic solves 90% with only red remaining.

From here you have a red 2 remaining in each of R21-30, a red 1 remaining in C19 and C29, and a red 2 in each of C20-28. Due to the offset of the available grid, I can see that the only way this is going to work is to start at R21C19 and end at R30C29. Unfortunately I'm having trouble spelling out the logical process for this one, so I'm not going to make a definitive ruling just yet.

I ended up in the exact same boat as Wombat. Can we agree to just call this last bit zigzag logic?

Sure, Michael, we used to have Aldege's beard logic, and when the going gets tough I've sometimes used experience logic, so why not zigzag logic? Although in this case I thought it was EL, which is classified as moderate lookahead, starting at R30C29 and reversing Wombat's direction to end at R21C19.

EL doesn't work here because any given move after any given placement still works; the contradictions always start at least 2 moves ahead. I could do some recursive work on the various placements on R30 to eventually narrow it down to C28-29, but the only possible placement I could eliminate within a "moderate" number of steps was C27-28. My method technically counts as deep but I'm hoping someone can come up with a truly moderate approach.

When I got down to those last reds, because of the red 1 in each of C19 and C29, and everything else being 2, the only possibility was for the locations of each red 1 to occupy R21 and R30.

If the C19 red 1 were R30, then the black 3 on C22 would contradict it. Thus, C19 red 1 could only be R21. The rest is just following the stair logic of the 2s.

Show: Spoilers

Goto next topic

You must register and log in to be able to participate in this discussion.