From: w_a_x_man <w_a_x_man@...>
Date: 2010-10-25T06:54:54+09:00
Subject: Re: Convert Array to nested Hash

On Oct 24, 6:07 am, Robert Klemme <shortcut...@googlemail.com> wrote:

>
> irb(main):019:0> [
> irb(main):020:1*   ["A", "a", 1],
> irb(main):021:1*   ["A", "b", 2],
> irb(main):022:1*   ["B", "a", 1],
> irb(main):023:1*
> irb(main):024:1* ].inject({}) do |h,(k1,k2,v)|
> irb(main):025:1*   (h[k1] ||= {})[k2] = v
> irb(main):026:1>   h
> irb(main):027:1> end
> => {"A"=>{"a"=>1, "b"=>2}, "B"=>{"a"=>1}}
>
> and another one
>
> irb(main):028:0> [
> irb(main):029:1*   ["A", "a", 1],
> irb(main):030:1*   ["A", "b", 2],
> irb(main):031:1*   ["B", "a", 1],
> irb(main):032:1*
> irb(main):033:1* ].inject(Hash.new {|h,k|
> h[k]=Hash.new(&h.default_proc)}) do |h,(k1,k2,v)|
> irb(main):034:1*   h[k1][k2] = v
> irb(main):035:1>   h
> irb(main):036:1> end
> => {"A"=>{"a"=>1, "b"=>2}, "B"=>{"a"=>1}}
>


a = [ ["A", "a", 1],
      ["A", "b", 2],
      ["B", "a", 1] ]
h = Hash.new{|hash,key| hash[key] = {} }
a.each{|x,y,z| h[x][y] = z}