UKPC 2013 Preview

[kiwijam]

Welcome to the First Annual UKPC Preview.
This idea is based on the excellent discussions held before the USPC contests of recent years, primarily lead by Thomas and Palmer.
There is a list containing the new (and less common) puzzle types coming up at the end of next week. Everyone can vote for the ones they'd like to see more of. And I'll create some examples of the popular ones over the coming week.

But anyone is welcome to join in. If you want to contribute a puzzle, or point out locations of other practise material, then please do!
If you want to ask for tips, or need help to solve an example puzzle from the instruction booklet, this is the place for that too.
Happy puzzling!

[kiwijam]

Rectangles With A Wall

At first I thought this variant looked a lot like Shikaku, fitting rectangles in together. And it is.
But it also uses some strategies from Nurikabe, keeping the pieces of black path connected, and making sure that a rectangle covers at least part of every 2x2 square.
There's a couple of basic things to do:
- For each hint, work out where that rectangle could fit. If there's only one option (more likely to happen for prime numbers) mark it in. If there are multiple options then check for any cells which are included in all of them.
- Shade in cells that no rectangle can reach. If you have 3 shaded cells in a 2x2 area, then find a rectangle to cover the fourth cell. This is more likely to occur if the number/size of hints is small.
- Don't create a wall of rectangle cells (including the given hint cells) that separates the grid into two parts, unless you can fill one of those parts completely with white rectangles and so leave the black cells in the other part.
And if you can't think of anything better to do, you can subtract the sum of the hints from the grid size, this will tell you the total number of black cells (maybe only useful if it is very small).

Here is a simple example that follows these ideas:

Rectangles With A Wall example 1

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[yureklis]

You can find Rectangles with a wall in here: http://yureklis.wordpress.com/2013/03/1 ... kach-2013/

[PSite]

I'll link to the place where I first saw Yosenabe puzzles.

http://nikolikeipuzzle.blog.fc2.com/blo ... -1696.html

That's the latest (17th) Yosenabe on that blog. It's easy enough to see how to go backwards in the links below the puzzle.

I don't have any practice available for True-False Snake because that inclusion in the set I sent was pretty impulsive, but I'll say that I got the idea from Yajisan Kazusan, and if you haven't solved that at all, then there's some tricks one can learn from solving those as far as liar logic in general goes. YKs are easily available, on my and Palmer's blogs.

[kiwijam]

You can find Rectangles with a wall in here: http://yureklis.wordpress.com/2013/03/1 ... kach-2013/

Thanks Serkan, that's a better Rectangles puzzle, I didn't know you'd made one. It uses the same logical approach: stretch out rectangles far enough to stop any 2x2 wall, but not too far that it cuts the wall off.

Serkan has generously provided 6 of the UKPC puzzles, and examples of the others can also be found at the same blog.
There is another Summon puzzle there that uses more 'Star Battle' logic, hopefully the UKPC puzzle is not that tough though.
And with Weather Symbols I still get muddled with my notations, keeping track of whether a cell is fixed yet, or which options are left.
I like the stories behind the puzzles, e.g. these really are used as weather symbols in Japan: http://commons.wikimedia.org/wiki/Categ ... s_of_Japan

[kiwijam]

[quote="PSite"]I'll link to the place where I first saw Yosenabe puzzles.
http://nikolikeipuzzle.blog.fc2.com/blo ... -1696.html
quote]

Wow, great link Prasanna!
I'd googled for "Yosenabe" without any luck, the rules are a little strange at first and I was hoping to find an example. I have some nikoli magazines from last year, but it may be too new for them.
Obviously next time I should try googling for "よせなべ"!

And it's a great puzzle blog that I never knew about too.
From the links on the right I see there are 1600+ puzzles there, with over 30 common and less common types (Creek, Country Road, Slitherlink, the English names are written using Japanese letters).
Google Translate can convert the whole page to something 'readable'.

[PSite]

Yea it's a nice blog in general. It gets updated with 2-3 new puzzles daily, and there's online solving for all.

[kiwijam]

Yosenabe

Today I've got a small Yosenabe puzzle for you to unravel.
If there are many grey areas, then you need to find which greys only have one circle that can reach them.
If there are few grey areas, then you need to find which circles only have one possible grey area available.
And there's always some basic addition to keep in mind when a grey area includes a sum target.

Yosenabe 1

Yosenabe 1.png (11.69 KiB) Viewed 33212 times

[kiwijam]

True/False Snake

The general strategy here is to consider each clue: what happens if it's white, what happens if it's shaded. Hopefully one of them gives a contradiction, although some clues won't tell you anything useful until the end.
It can also be useful to look at pairs of clues when they point along the same column, or along adjacent columns. Ask if they're both white, is there enough room to shade in the required number of cells? A snake cannot cover all of a 2x2 square, so can only cover three quarters (approximately) of a 2xN strip.

Here's a True/False Snake puzzle. Actually it's two puzzles. I was quite surprised at how different the solutions could be given a tiny change in the clues.
This will be the second-hardest type of the contest, so hopefully the difficulty is similar.

If you need help getting started:

PRIME_BBCODE_SPOILER_SHOW PRIME_BBCODE_SPOILER:

Start with the 1,6,4,3 clues in that order, they should eventually give you most of the left three columns. Then look at the two cells that swap between a 5-clue and a 6-clue, what colours can they be?

True/False Snake puzzles

TrueFalse Snake.png (12.77 KiB) Viewed 33172 times

PS If you want to check your answer, you can do so at http://www.logic-masters.de/Raetselport ... ?id=0001RB.

[kiwijam]

That'll be my last puzzle before the weekend.
Hopefully they've been helpful and I'm not just talking to myself!
Thank you to Prasanna and Serkan for providing links.
If anyone wants to create a Summon puzzle that'd be much appreciated too.
Anyway, enjoy the contest everyone.