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#1: Adam Nielson (monkeyboy) on May 13, 2009 [HINT] [SPOILER]

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Found to be logically solvable by jan.

I really liked this....but ONLY because it was chewable...any larger and the constant trial and error (what everyone seems to call edge logic) would have driven me nuts.

ANY solvable puzzle is "logically solvable" if one uses "edge logic" so I'm confused by the determination "logically solvable".

I still liked this puzzle because it was small enough not to take an age and a half to solve by trial and error.

Well, some people use the word "edge logic" quite liberally, and some of the puzzles they claim are solvable by "edge logic" don't appear to be so to me.

There is an explanation of edge logic on the "Advanced Puzzle Solving" page, but I probably have to revisit it, because a lot of people don't get it.

Suppose the first column of the puzzle has just one clue: "3".

Suppose the second column of the puzzle has the clue "1 1".

Big number along the edge, and smaller numbers further in, that's a sign that edge logic might work. To make it work, we look at the first numbers of all the row clues. Suppose all of them were 2 or larger.

Then we'd know the puzzle was erroneous and impossible to solve, because anyplace you placed the "3" in column one, the row clues would all fill in at least one cell in column two, and you'd have a three in column two, which can't be there. There can only be ones.

But suppose we look closer and fine one row clue that starts with a "1". Aha! We're saved. The three in column one can be placed straddling this "1" row, so in column 2 there'd be two blacks separated by a dot.

That's the pattern. You look at the placement of a block along (or near) the edge, in this case the 3 in column 1, and look for positions that are compatible with clues in some line a bit further inward (in this case column two). I find this very easy to do without needed to mark and undo. It takes a little counting and cross-checking, but so does regular line solving.

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Ditto Teresa!

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Nice puzzle

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great solve

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Tough to see.

This is the hardest little puzzle I've ever seen. I enjoyed it because I grew from it. I love advancing in logic. Although I didn't figure it out myself, Gator's explanation in his hint taught me something. I look forward to getting better at edge logic.

Aurelian - if that thought that little puzzle was hard, you should try #6302. http://webpbn.com/6302 :)

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so you enjoy that more than trying other forms of logic?

It boils down to a matter of knowledge; I enjoy WPBN-battleship more than I would seeking the knowledge of other forms of logic to apply, though I know they exist. :)

gotcha, i was just genuinely curious :) sounds a bit like when we'd get stuck in Minesweeper and there was no more logic, but a shot in the dark fingers crossed :)

One of the ways that PBN puzzles are better than Minesweeper. :)

Yaaaaas! A wrong click doesn't end the game!

One of my kids found an online multiplayer Minesweeper game that was really intriguing to play -- an interesting mix of cooperativeness and competitiveness, playing against a small handful of people from all over the world. But I don't think it's around anymore -- the URL where it used to be now brings up something else instead.

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