organizing_number_pairs_problem.rb

# I need your help geeks. ;)
# I have an array of items
# Some items have a number on both sides
# I'll call these "matched pairs".
# The matched pairs are the keystones of this problem.
# I need to sort the items between the matched pairs
# in a particular way.


# There's a "from number" and a "to number"
# There may be more from -> nil than 
# nil-> from. It may be the other way around.
# There may also be NO items 

# I have this
#   v from number
#          v to number
[
	[nil,  1],
	[1,    2],  # a matched pair
	[2,    nil],
	[3,    nil],
	[4,    nil],
	[5,    nil],
	[nil,  3], # note that there are more 
	[nil,  4], # nil -> to number than 
	[nil,  5], # from number -> nil
	[nil,  6],
	[nil,  7], 
	[6,    8],  # another matched pair
	[7,    9],  # nothing in between
	[8,    nil],# no nil->to number to pair it with
	[9,    10]

]

# i need to transform it to this

[
	[nil,  1],
	[1,    2],
	[2,    nil],
	[nil,  3],
	[3,    nil],
	[nil,  4],
	[4,    nil],
	[nil,  5],
	[5,    nil],
	[nil,  6],
	[nil,  7],
	[6,    8],
	[7,    9],
	[8,    nil],
	[9,    10]

]