

25 Dots, 8 Lines - hliaskal
http://e-riddles.blogspot.gr/2013/04/25-dots-8-lines.html

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TranceMan
Spoiler - interesting solution [from the comments]:
[http://www.scribd.com/doc/133494020/Extended-9-dots-
puzzle-t...](http://www.scribd.com/doc/133494020/Extended-9-dots-puzzle-to-
nx2-dots)

Solved mathematically :)

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Someone
Where's the 'solved' part? At the very best, he shows that you can do it with
2 _n-2 lines. Even that includes a lot of hand waving/implicit "it is easy to
see"-s.

That you need 2_n-2 lines, he doesn't talk about at all.

~~~
danbruc
Additionally the OEIS now contains a wrong fact [1] - the sequences are offset
by one. I am not even convinced that 2n - 2 is optimal - does somebody know if
it is or can proof a better lower bound than the trivial n?

[1] <http://oeis.org/A058992>

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mkl
I left a hill-climbing solver running overnight and found quite a few
solutions, including a couple that can be made to stay inside the square:
<http://imgur.com/a/Wd2dS>

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kaoD
I can solve it with just 5 lines. You just have to get the pen to infinity and
then come back.

Wait, if infinity wraps around that'll take just one line!

~~~
yk
I am pretty sure that it is meant to be solved on a compact, simple connected
subset of |R^2, with Euclidean metric.

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S4M
Careful with that. If the frontier of that subset is not far enough from the
points, the problem will not be solvable.

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yk
And probably the word 'open' is also missing, then I can always find an
embedding such that there is enough room :)

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twiceaday
My solution: <http://i.imgur.com/z2mo2Jj.jpg>

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tydok
My solution <http://i.imgur.com/S2L9pht.jpg>

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Strilanc
Solution (rot13):

Whfg genpr nebhaq gur bhgfvqr gura hfr gur fbyhgvba gb gur fznyyre chmmyr.

~~~
pdevr
Great. Keeps it simple.

On a side note, can anyone build a cool ROT13 converter? There are some, but
they are showing their age.

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mdellabitta
Why do you need 8 lines? You just need 5 lines, and an enormous piece of
paper.

EDIT: Beaten to the punch. I should learn to read comments first.

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panacea
It doesn't specify that you can't add curved lines between your straight lines
without lifting your pen.

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frooxie
It's possible to solve it entirely "within" the box.

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petterjohnson
What? kindly explain a little..

