From: CT <demerzel@...>
Date: 2004-07-11T17:22:53+09:00
Subject: Re: A little algorithmic help requested...

Hiya,

I may not have read you correctly, but does this do what you seek?
--
require 'pp'
a = [1,2,3,4,6,7,8,11,12,15,16,17]
pp a.inject([[a.shift]]) {|arr,i|
				temp = arr.last
				if(temp.last.next == i)
					temp << i
				else
					arr << [i]
				end
				arr
			}.inject([]) {|arr,i|
						if(i.length >= 3)
							arr<<(i.first..i.last)
						else
							arr = arr + i
						end
					}
--
Gives me: [1,2,3,4,6,7,8,11,12,15,16,17]
First inject collects all consecutive ranges into sub-arrays, second
one converts these to ranges/flattened arrays.
corrections/improvements are welcome.
HTH
- CT

On Sun, 11 Jul 2004 16:10:34 +0900, Hal Fulton <hal9000@hypermetrics.com> 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?
> 
> Thanks,
> Hal
> 
>