Puzzle Description:

A compass rose.

#1: Joe (infrapinklizzard) on Dec 20, 2011

Try to use summing logic to finish this - there's a cool way (if you're a geek like me) to do it. Otherwise it's a 2-step look-ahead.

Line logic gets you halfway done. Then there's some look-ahead that needs to be done. I haven't found any straightforward edge, smile, or two-way logic.

The most normal, and least-look-ahead solve to this that I've found is to look at one of the 3s. Let's pick the 3 in r4.

If it goes all the way to the right, then the pixels directly below and above need to be white (c5-r3&5). The across clues then force both c4-r3&5 to be black. That's a conflict with c4, so r4c5 must be white.

Then line logic to finish.

===

The much more fun summing method is thus:

Look at rows 1-2. There are a total of 3 black pixels yet to be set. Now look at c1. There's one pixel that must be in r1-2.

So now we know there must be two pixels in r1-2, c2-5.

Look at c3. Again, there's one pixel that must be in r1-2. That means that the last of the three pixels must be in either r1c2 or r1c5.

To put that statement another way, *either* r1c2 *or* r1c5 must be black, *but not both*.

If you choose to put a black in r1c2, you can immediately see that r1c5 would also have to be black, so r1c2 must be white.

Then line logic to solve.

A great small puzzle Joe, I think I am to old to be a geek so I solved it with logic.

Great small puzzle Joe....that's a lot of summing for a small puzzle! I confess, I guessed at the end!

a waste of time, but at least it was a very short waste of time.

a waste of comment, but at least it was a very short waste of comment.

Thanks, everyone else.

very fun solve
very funny reply in 6, to 5

Like others who enjoy logic puzzles, I thought this was GREAT fun! It was kind of like mental calisthenics, and was very rewarding to figure out.

I used regular edge logic on the upper right corner. I had to look ahead a few steps, but since the grid is so small, it wasn't too difficult.

After a little bit, I just guessed. Very fun though!

after LL this was my look-ahead move (that is based on two-way logic)...

looking at the 2 in C4, which ever way it went either C5R3 or C5R5 would be a dot making C5R1 a black.

Very good, David. I like it!

Thanks, all.

No guessing of course, and I did it like David!

Found to be solvable with moderate lookahead by jan.

Lol #6. Very witty.

Goto next topic

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