Friday Puzzle #36 - 2010 Masyu

[motris]

Coming in a tie for first (but reaching first second) in my poll was Masyu, so by popular acclaim I bring you a 2010 Masyu. Masyu just happens to be the topic of the current GAMES Magazine PuzzleCraft article (April 2010) if you want to see some more themed Masyu I've written and read about how to construct them

Comments

[anonymous]

The whites aren't too far from reading as "zulu" - I guess that's a "pixelation" effect.

The good bits were 1) the "cornered corridors" you had to avoid creating, 2) the closed loops you had to avoid creating with the wrong orientation of a line through a white and 3) the cute trick on the second black 0.

Interestingly, this is all non-sledgehammer logic as I understand it; the deductions you make are all arrived at via rejections of alternative hypotheses because they lead to an implicit rather than explicit contradiction of the rules.

Tom.C

[motris]

The cute trick on the second black 0 is my favorite part, specifically the white cell near the top that must be crossed, but whichever way it crosses will form a connection to the cell to the lower-right and therefore force the bottom groups downwards. I'd argue this is less an example of rejecting alternative hypotheses so much as a masyu equivalent of painting where whichever thing happens, a particular connection will eventually be made. Unfortunately, using uniqueness on that side of the puzzle bypasses the logic of this step.

[thesubro]

The thing about uniqueness techniques in the context of such a nice puzzle is that you feel as if you are cheating the designer. When I come across them in a situation like this, I tend to note them but not commit to them. Then I go about my business drilling down into the area that will have to change to make the solution incapable of getting to a non-unique solution without using uniqueness alone as the factor. It is probably why I am the Snail in this group, but I want to enjoy that which the designer intended to create.

Great Masyu. Great pair of 2010 puzzles.

Ken

[anonymous]

I'd agree with that philosophy, as long as there isn't some sort of time competition going on (which is to say I'll totally abuse meta-logic on competitions but not for this sort of puzzle unless I can't figure out the "real" solution).

For me, I wasn't tempted to use uniqueness to solve this Masyu, but I definitely ran into that temptation on the preceding Yajilin. The situation in that puzzle (which came up like 3 times) is that you have a corridor 2 squares wide and a pair of loose path ends on each side. It has to go ===== rather than ==)(== since the location of the turn wouldn't be unique.

[tualha]

Are you all quite sure this has a solution? I've tried solving it several times, and I keep hitting the same problem. I'm pretty sure it has no solution.

[motris]

I'm sure it has a single valid solution; I tried to quickly sketch it out here.

[tualha]

Ah! Thank you. I had thought that going down from the black circle would force a subloop, but overlooked (three times!) a way to avoid it.