From: Todd Benson <caduceass@...>
Date: 2007-06-19T03:41:05+09:00
Subject: Re: Adding new value (in array) to existing key in a hash

On 6/18/07, Gilbert Lau <gilbertlsk@gmail.com> wrote:
> Thanks a million. But still I have another problem. Figure that I can
> take it on from all your guys' help, but I can't.
>
> A more controlled sort. I only want to sort the keys where the values
> from myhash follows this pattern of [i,j], [i+1,j+1]...  think of it as
> a 2-D matrix and I am only interested in the diagonal line. I am not
> worried about the duplicates of coordinates, as one coordinates can only
> have one occurrence(or building).
>
> For example, the sorted result for the following hash will be:
>
> myhash = {"a"=>[[0, 0], [3, 4]], "b"=>[[1, 1], [9, 8]], "c"=>[[7, 6],[4,
> 5]}
>
> [[0, 0], [1, 1], [3, 4], [4, 5]]
> "a", "b", "a", "c"

Do you mean that [7,6] is not included becuase there is no [6,5] or
[8,7]?  You shouldn't open up core classes and you don't have to for
this, but it makes it more readable:

class Array
  def up; map {|i| i+1}; end
  def down; map {|i| i-1}; end
end
h = { "a" => [[0,0],[3,4]], "b" => [[1,1],[9,8]], "c" => [[7,6],[4,5]] }
a = []
h.each_value {|v| v.each {|coord| a << coord}}
end
sorted = a.select {|coord| a.include?(coord.up) ||
a.include?(coord.down) )}.sort

p sorted