johnmcdonald.rb

#
# average_time_of_day(arrival_times)
#  arrival_times is an array of times, e.g
#    ["11:51pm", "11:56pm", "12:01am", "12:06am", "12:11am"]
# code calculates the average of the array of the times of day
#
# start time is implied to be any time of day, am or pm, so
# the code will work just using Time.now as a start time
# if start time is 'am' all times are assumed to be the same day
# if start time is 'pm' all 'am' times are assumed to be the next day
# 
require 'time'

def average_time_of_day(arrival_times)
  calc_average_time(arrival_times)
end

def calc_average_time(arrival_times)
  avg_time = 0
  start_time = Time.now
  am_or_pm = start_time.strftime("%p").downcase
  number_of_times = 0

  arrival_times.each { |item| item.gsub(/^([0]*[1-9]|[1][0-2]):([0-9]{2})([a|p]m)/) do   
      arrival_time = Time.parse($1 + ":" + $2 + $3)
      number_of_times = number_of_times + 1
      case
        # add a day if time is 'am' and start time is in the 'pm'
        when am_or_pm == "pm" && $3 == "am" then arrival_time += (60 * 60 * 24)
      end

      avg_time +=  arrival_time - start_time
      #puts start_time, arrival_time, avg_time
    end
  }
  raise "Bad time entered: check input " unless number_of_times == arrival_times.size
  (start_time + avg_time/arrival_times.size).strftime("%I:%M%p")
end

#p average_time_of_day(["11:51pm", "11:56pm", "12:01am", "12:06am", "12:11am"])