Solution to the 'Datacenter Cooling" problem:
============================================

This problem is on the quora.com 'job challenges':

We have some rooms in our datacenter, and we need to connect them all with a
single cooling duct.

Here are the rules:

1. The datacenter is represented by a 2D grid.
2. Rooms we own are represented by a 0.
3. Rooms we do not own are represented by a 1.
4. The duct has to start at the air intake valve, which is represented by a 2.
5. The duct has to end at the air conditioner, which is represented by a 3.
6. The duct cannot go in multiple directions out of the intake or the AC - they
   must be the two endpoints of the duct.
7. The duct must pass through each room exactly once.
8. The duct cannot pass through rooms we do not own.
9. The duct can connect between rooms horizontally or vertically but not diagonally.

The challenge is "How many ways are there to pass the duct?"

Instructions: 
============ 
Written and tested on Linux machines. :)

Written in C with no dependencies.
Just run make, and run the executable 'duct'.

Usage:
./duct < <grid file>

The grid file describes the grid as follows:

A list of integers separated by whitespace.  The first two are the width and
height in that order.  And then a width*height integers that describe the grid
as follows:

0 - Rooms owned by us
1 - Rooms not owned by us
2 - Start room
3 - End room

The program just prints out one integer.  If you want it to print out solutions
as it finds them compile with option '-DPRINT'. Just add it to the makefile
variable CFLAGS. 

There's a 'sample' file with the program for an example input.  The
'quora_sample' file is the input quora.com suggested. (very complex)

Comment:
========

This solution ran just under one minute for the input Quora gave on their
website, on a 2.4 GHz linux machine.

You can reach me at:
sadanjon at gmail dot com


Files
=====
|-- duct.c
|-- duct.h
|-- grid.c
|-- grid.h
|-- Makefile
|-- node.c
|-- node.h
|-- queue.c
|-- queue.h
|-- sample
|-- README
`-- util.h