Snake-cube solver

Brute-force solver for snake-cube puzzle. More info here or see video here.

Input specification

Tool consumes an input string from stdin. Alphabet consists of two characters:

• R - horizontal joint (going from left to right)
• D - vertical joint (going from up to down)

Input has to contain exactly 26 characters (that's number of cubes minus one), no whitespaces inside the sequence.

How to represent your snake-cube puzzle

Unwind whole snake puzzle and put it flat on the table so that it goes from top-left to bottom-down. You should see something like this:

XXX
  XX
   XX
    XX
     XX
      X
      XX
       XX
        XX
         XXX
           X
           XX
            XX
             X

Starting from top-left for each joint, write use R or D depending on whether it is horizontal or vertical. So you end up with this:

RRDRDRDRDRDDRDRDRDRRDDRDRD

This is the input string for a solver.

There is a helper python script drawing2rd.py that transforms the 'drawing' format to the R/D format. Have a look at example.drawing and example.rd files. You can produce latter from the former by invoking:

cat example.drawing | python drawing2rd.py

Implementation and usage

There are two implementations currently:

• snake_cube.py - Simple python implementation. It is slow and does not de-duplicate results.
• snake_cube.scala - Scala script, better optimized, prints out all unique solutions.

Example of invoking the solver:

echo RRDRDRDRDRDDRDRDRDRRDDRDRD | python snake_cube.py
echo RRDRDRDRDRDDRDRDRDRRDDRDRD | scala snake_cube.scala

Output will look like this:

Found solution:
  0  1  2
 23  4  3
 22  5  6

 25 26 13
 24 15 14
 21  8  7

 18 17 12
 19 16 11
 20  9 10

This is a representation of the final cube (3 x 3 in 3 layers). Numbers represent individual pieces starting from the top left corner of the input - i.e. 0 is the top-left piece, 1 is the second one...

This can be quite easily used to solve the real 'physical' puzzle.