Problem #130

Perfectly protected pillars
Public 06/27/14 10xp Programming 61.5%

In the main hall of the King's palace there are pillars disposed in a rectangular grid N*M

The king wants to dispose 4 guards at the 4 directions of each pillar.
A guard at the east of a pillar is at the west of the next pillar, etc ...

Being mathematically inclined, the king wants that for each pillar, there are exactly 2 guards looking at it and 2 guards turning their back.

Here is an example with 2*3 pillars (and 17 guards):

How many possible configurations are there for 4*6 pillars?

You are given: 374 configurations for 2*3 pillars
[My timing: 25 sec]

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