From: raja@... (Raja S.)
Date: 2001-11-30T15:36:24+09:00
Subject: [ruby-talk:27034] Re: Help: factored sorting

Bil Kleb <W.L.Kleb@LaRC.NASA.Gov> writes:

>I have an array of strings,

>a = ["d3", "d33", "d4", "r16", "r33", "d34", "r34"]

>which I'd like to sort by both the numerical suffix and by
>the alphabetic prefix, i.e., I'd like the result,

> ["d3", "d4", "d33", "d34", "r16", "r33", "r34"]

>or, even better would be an array of two prefix-keyed
>sub arrays that I could exploit with the assoc method,
>viz,

> [ ["d", "d3", "d4", "d33", "d34"], ["r", "r16", "r33", "r34"] ]

Hmmm ... thinking about the later part,  seems easier to split it into two:

1.  the sorting described in an earlier note followed by

2. a "gathering" phase:

def gather( sorted_ary )
  hsh = {}
  sorted_ary.each do |x|
    primary_key = keys(x).first
    if hsh.has_key?(primary_key)
      hsh[primary_key] << x
    else
      hsh[primary_key] = [primary_key, x]
    end
  end
  result = []
  hsh.keys.sort.each do |key|
    result << hsh[key]
  end
  result
end

gather( a.sort{ |x,y| keys(x) <=> keys(y) } )

regards,

Raja