August 2015

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Ponder This Challenge:

Find a way to fold a loop of string in three-dimensional space such that all three projections will be loop-free (i.e., you won't be able to make a path from a point to itself without backtracking).

Provide your answer as a list of integer 3D coordinates, where each pair differs in exactly one coordinate.

For example, the following list is loop-free on two projections (x,z) and (y,z), but forms a loop on the third projection (x,y):

[1,1,1],[1,1,2],[2,1,2],[2,1,1],[2,2,1],[2,2,2],[1,2,2],[1,2,1],[1,1,1].

Update (18/8):

The 3D loop should be non-trivial, so [1,1,1],[1,2,1],[1,1,1] is not a valid solution.

We will post the names of those who submit a correct, original solution! If you don't want your name posted then please include such a statement in your submission!

We invite visitors to our website to submit an elegant solution. Send your submission to the ponder@il.ibm.com.

If you have any problems you think we might enjoy, please send them in. All replies should be sent to: ponder@il.ibm.com