Good evening,
For those of you who were at the world championships and got a UFO puzzle, this
might
be interesting. Wes and I wrote an interactive solver for it. You can find it at
<http://www.terpstra.ca/puzzles/ufo.php>
By clicking the pieces from the right UFO, you can move them (via the middle)
to the left
UFO. Once the left UFO is completely filled up, the program will find a
move-optimal
solution.
Interesting facts about the puzzle include:
There are exactly 11! distinct states (12* more if you hold it differently)
- the included booklet is wrong by 800 states for whatever reason
Every state is reachable (all moves are odd permutations, so even/odd are
both
reachable)
The longest distance between any two states is 16 moves
Interesting facts about the solver include:
It only needs to explore 11 thousand states on average
It's written in Standard ML (compiled by MLton.org) and PHP
On a decent machine (not that webserver), it needs < 1s
Some useful operations are:
flip two neighbours <http://www.terpstra.ca/puzzles/ufo.php?
gyr=0&grb=1&ggo=2&gbg=3&gop=4&gpy=5&bry=6&bbr=7&bgb=8&bog=9&bpo=10&b
yp=11>
flip top and bottom pieces <http://www.terpstra.ca/puzzles/ufo.php?
gyr=0&grb=1&gbg=2&ggo=3&gop=4&byp=5&bry=6&bbr=7&bgb=8&bog=9&bpo=10&g
py=11>
... notice that these are really far apart states. :-)
Have fun,
Maria
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