From: Michael Neumann <mneumann@...>
Date: 2004-07-12T02:09:47+09:00
Subject: Re: A little algorithmic help requested...

On Sun, Jul 11, 2004 at 04:10:34PM +0900, Hal Fulton wrote:
> Here's a problem my tired brain is having trouble with.
> 
> Given a sorted array of integers, convert them into as many
> ranges as possible (ranges of three or more).
> 
> Example:
> [1,2,3,4,6,7,8,11,12,15,16,17] ==> [1..4,6..8,11,12,15..17]
> 
> How would *you* do this?

  require 'enumerator'

  def to_range(arr)
    ranges = [r=[]]
    arr.each_cons(2) {|a,b| 
      r << a
      ranges << (r = []) if (b-a) != 1
      r << b
    }
    ranges.map {|r| 
      r.uniq!
      r.size > 2 ? (r.first..r.last) : r 
    }.flatten
  end

  a = [1,2,3,4,6,7,8,11,12,15,16,17]
  p to_range(a)

But no, I wouldn't do it this way.

Regards,

  Michael