Perfectly protected pillars
C_K_Yang liuguangxi a_forsteri Min_25 stubbscroll C3PO Philippe_57721 gerrob zilet sinan lesnik7 Caesum Buri dloser
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]
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):
↓  ↑  ↑  
←  O  →  O  →  O  ←  
↑  ↑  ↓  
→  O  →  O  →  O  →  
↑  ↑  ↓ 
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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