How to combine overlapping time ranges (time ranges union)

The facets gem has Range.combine method that may be of use: http://rdoc.info/github/rubyworks/facets/master/Range#combine-instance_method

You can do it by using multi_range gem.

Example 1:

ranges = [
  Time.parse('Tue, 24 May 2011 08:00:00 CEST +02:00..Tue')..Time.parse('24 May 2011 13:00:00 CEST +02:00'),
  Time.parse('Tue, 24 May 2011 16:30:00 CEST +02:00..Tue')..Time.parse('24 May 2011 18:00:00 CEST +02:00'),
  Time.parse('Tue, 24 May 2011 08:00:00 CEST +02:00..Tue')..Time.parse('24 May 2011 09:00:00 CEST +02:00'),
  Time.parse('Tue, 24 May 2011 15:30:00 CEST +02:00..Tue')..Time.parse('24 May 2011 18:00:00 CEST +02:00'),
]

MultiRange.new(ranges).merge_overlaps.ranges
# => [2011-05-24 08:00:00 +0800..2011-05-24 13:00:00 +0800, 2011-05-24 15:30:00 +0800..2011-05-24 18:00:00 +0800] 

Example 2:

ranges = [
  Time.parse('Tue, 24 May 2011 08:00:00 CEST +02:00')..Time.parse('Tue, 24 May 2011 13:00:00 CEST +02:00'),
  Time.parse('Tue, 24 May 2011 16:00:00 CEST +02:00')..Time.parse('Tue, 24 May 2011 18:00:00 CEST +02:00'),
]

MultiRange.new(ranges).merge_overlaps.ranges
# => [2011-05-24 08:00:00 +0800..2011-05-24 13:00:00 +0800, 2011-05-24 16:00:00 +0800..2011-05-24 18:00:00 +0800] 

Searching a little bit I have found a code that does the trick:

def self.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

A sample (working with time ranges too!):

ranges = [1..5, 20..20, 4..11, 40..45, 39..50]
merge_ranges(ranges)
=> [1..11, 20..20, 39..50]

Found here: http://www.ruby-forum.com/topic/162010

Given a function that returns truthy if two ranges overlap:

def ranges_overlap?(a, b)
  a.include?(b.begin) || b.include?(a.begin)
end

(this function courtesy of sepp2k and steenslag)

and a function that merges two overlapping ranges:

def merge_ranges(a, b)
  [a.begin, b.begin].min..[a.end, b.end].max
end

then this function, given an array of ranges, returns a new array with any overlapping ranges merged:

def merge_overlapping_ranges(overlapping_ranges)
  overlapping_ranges.sort_by(&:begin).inject([]) do |ranges, range|
    if !ranges.empty? && ranges_overlap?(ranges.last, range)
      ranges[0...-1] + [merge_ranges(ranges.last, range)]
    else
      ranges + [range]
    end
  end
end