paulbarry.rb

require 'time'

# Monkeypatching FTW! ;)
module Enumerable
  def sum
    inject(0){|acc,e| acc + e}
  end
  def avg
    size > 0 ? sum / size : 0
  end
end

class Time
  ONE_DAY = 60 * 60 * 24
  
  # Returns a 3 element array containing
  # - the time (self) minus one day
  # - the time (self)
  # - the time (self) plus one day
  def plus_or_minus_one_day
    [self - ONE_DAY, self, self + ONE_DAY]
  end
  
  # Given an Array of Times, this will returns 
  # a time representing the average all the times
  def self.avg(times)
    Time.at(times.map{|t| t.to_i}.avg)
  end
  
  # Given an Array of Times, this will return
  # the time in the Array that is closest to this Time (self)
  def closest(times)
    if times.empty? then self else
      times.min{|a,b| (self - a).abs <=> (self - b).abs }
    end
  end
  
end

def average_time_of_day(times_of_day)
  Time.avg(times_of_day.inject([]) do |times, time_of_day|
    time = Time.parse(time_of_day)
    avg = times.empty? ? time : Time.avg(times)
    times << avg.closest(time.plus_or_minus_one_day)
  end).strftime("%l:%M%p").downcase.strip
end

if __FILE__ == $0
  puts average_time_of_day(["11:51pm", "11:56pm", "12:01am", "12:06am", "12:11am"])
  puts average_time_of_day(["6:41am", "6:51am", "7:01am"])
end