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Sunday, Nov 6
drnull
Kwon-Tom Obsessive
Puzzles: 901
Best Total: 23m 25s
Posted - 2005.11.08 23:09:52
Hey guys, thanks for the fun puzzles.  I saw slither link puzzles a while back, and enjoyed them, but ran out of them too quickly.  These help quell my addiction.

Anyway, I was doing decent with the times on these puzzles till I got to Sunday, Nov 6.  This one blew me away.  I've tried it again, and again, I am stuck at more or less the same place I got stuck last time.  I got it last time by trying different 1's and 3's till it didn't work, then x'ing out that try.  It took a really long time that way.  Surely I'm missing some obvious rules here?

um, image removed... I didn't think about the fact that maybe some people haven't done this puzzle yet.

Also, are you guys able to solve without using the fix/reset to fixed method?  I often see good patterns (like 3 next to 1 on a wall, etc) but just feel like I'm missing something since I often have to try random paths and see if they fail.

Thanks.
Last edited by drnull - 2005.11.08 23:26:36
foilman
Kwon-Tom Admin
Puzzles: 1720
Best Total: 24m 8s
Posted - 2005.11.09 08:52:55
Hi drnull! Glad to hear you're enjoying the puzzles, like you I did the few Slither Link puzzles I could find on the web, then wanted some more - so I wrote some code that generates them for me and puts them on my web site (ie this one). That's why you're all here, I thought "other people might like to do these too..."

Anyway, it's possible to solve all of the puzzles without using the "fix position" functionality, but it helps to have a brain the size of a planet... I've often printed puzzles off to do in airports & on long flights, and there are times I'm sitting there thinking many moves ahead, trying to work out what the consequences of a particular line or cross might be. Difficult, but possible - ultimately, of course, the "fix position" is an easier way of doing the same thing. Especially if you're aiming for a decent solving time.

There are lots of really obscure patterns to look for, but you do really only pick them up after solving lots, before that it's just applying logic. I find these days I'm more often looking for situations which would result in sections of the puzzle becoming blocked off, or with too many lines going into one area.

Something you might not have thought of is that any route traced from an edge on one side of the puzzle to an edge on another, has to cross an even number of lines (whether it goes direct or not). I don't use that rule very often, but it's come in handy a few times.
Helge
Kwon-Tom Obsessive
Puzzles: 3021
Best Total: 11m 26s
Posted - 2005.11.09 09:21:48
I really enjoy this site too! And I always have problems with the Saturday and Sunday puzzles.

Here's a link to some pretty useful hints:

http://www.puzzle.jp/keys/slitherlink_keys-e.html

Good luck.
Last edited by Helge - 2005.11.09 09:22:20
astrokath
Kwon-Tom Obsessive
Puzzles: 3093
Best Total: 13m 42s
Posted - 2005.11.09 10:36:47
Quote:
Originally Posted by foilman

There are lots of really obscure patterns to look for, but you do really only pick them up after solving lots, before that it's just applying logic. I find these days I'm more often looking for situations which would result in sections of the puzzle becoming blocked off, or with too many lines going into one area.
Ditto.

The usual tactics I apply for the larger puzzles are to begin with the obvious - 0's, groups of 3's or 1's, obvious closed loops etc.  I use the fix-pattern button regularly - there's no way I could hope to solve the puzzles quickly without it!

When it comes to making guesses/tracking down the correct route, I find the easiest option is to start with links that I'm fairlycertain will be wrong.  You can rule these out fairly quickly, making the correct route that much more obvious.  If you start with the right route, it's hard to tell whether it's correct or not, other than by continuing to make further guesses and hoping that you're lucky.  For Nov 6, I managed to close off a fairly large section of the puzzle reasonably easily this way, leaving a small unsolved region in the centre left, and a larger one extending from the centre to the top right corner.  The best method of solving these regions was finding the links that led to an early closed loop - separating out the left and right sides of the puzzles.  Obviously, any links which close the loop too soon are wrong!  This was a fairly tricky puzzle, and making certain that I had just a single loop and no stray ends was the most effective way of solving it.

Quote:
Originally Posted by foilman

Something you might not have thought of is that any route traced from an edge on one side of the puzzle to an edge on another, has to cross an even number of lines (whether it goes direct or not). I don't use that rule very often, but it's come in handy a few times.

Why havn't I noticed that before?  I certainly count up the stray ends and always aim to have an even number of them, but I've never thought of applying that to the number of lines crossing the distance between two sides. Thanks for the tip! 
drnull
Kwon-Tom Obsessive
Puzzles: 901
Best Total: 23m 25s
Posted - 2005.11.09 14:06:05
Quote:
Originally Posted by astrokath
For Nov 6, I managed to close off a fairly large section of the puzzle reasonably easily this way, leaving a small unsolved region in the centre left, and a larger one extending from the centre to the top right corner.  The best method of solving these regions was finding the links that led to an early closed loop - separating out the left and right sides of the puzzles.  Obviously, any links which close the loop too soon are wrong!  This was a fairly tricky puzzle, and making certain that I had just a single loop and no stray ends was the most effective way of solving it.

Thanks, that's roughly the same way I ended up doing that puzzle.  Just making sure that I wasn't missing some grand scheme of things idea. 

Quote:
Originally Posted by foilman

Something you might not have thought of is that any route traced from an edge on one side of the puzzle to an edge on another, has to cross an even number of lines (whether it goes direct or not). I don't use that rule very often, but it's come in handy a few times.

That is a handy method.  I actually used that once on the Nov 6 puzzle.  Handy that it works across any two side points, no matter how you get across the puzzle.

Thanks for the pointers, guys.  At least I know I'm on the right track.  Just need more patience.  Ugh, 16 minutes on today's puzzle.  I had brain freeze. 

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