From: "David A. Black" <dblack@...>
Date: 2008-08-07T08:00:32+09:00
Subject: Re: Need help detecting overlapping ranges

Hi --

On Thu, 7 Aug 2008, Bryan Richardson wrote:

> Hi David,
>
> I like the conciseness of your code, but I think it only works for when
> the end of one range is the same as the beginning of another.  I need to
> also handle the times when ranges overlap more than that (i.e. 1..5,
> 3..6 -> 1..6).  Thanks for thinking about this!

Here's the heavy artillery :-)

def merge_ranges(ranges)
   ranges = ranges.sort_by {|r| r.first }
   *outages = ranges.shift
   ranges.each do |r|
     lastr = outages[-1]
     if lastr.last >= r.first - 1
       outages[-1] = lastr.first..[r.last, lastr.last].max
     else
       outages.push(r)
     end
   end
   outages
end

require 'test/unit'

class RangeTest < Test::Unit::TestCase
   def test_one
     ranges = [1..5, 20..20, 4..11, 40..45, 39..50]
     assert_equal([1..11, 20..20, 39..50], merge_ranges(ranges))
   end

   def test_two
     ranges = [1..5, 7..11, 22..29, 5..8]
     assert_equal([1..11, 22..29], merge_ranges(ranges))
   end

   def test_three
     ranges = [1..5, 7..11, 22..29, 6..8]
     assert_equal([1..11, 22..29], merge_ranges(ranges))
   end
end


David

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