My solution was selected as the winning solution for’s RPCFN #2 “Average Arrival Time for A Flight.”

This challenge involved averaging times of the day without the actual day in the context.  When I first started to tackle the problem I thought to myself that this will be very easy.  Then I hit the “no day” context and realized that this problem was much tougher than I anticipated.  When I finally saw the posted solutions including Chris Strom’s (blog) it was like decades old high school math came rushing back to me.  I would have never thought of plotting points on a graph but now that I’ve been exposed I’m certain I will never forget it!

My friend [and commuting body] Matt and I talked through the problem during our drive home as we sat in Virginia I-495 outer loop and I-95S traffic.  He had some ideas about plotting the problem linearly around 0 but ultimately I ended up going with making assumptions about how close the provided times were to midday and midnight.

require 'time'

SECONDS\_IN\_DAY = 86400  
MIDNIGHT = Time.parse("12:00AM").to_i  
MIDDAY = Time.parse("12:00PM").to_i

def average_time_of_day(times)  
  seconds = []
  times.each {|time| seconds << Time.parse(time).to_i}
  if (seconds.first - MIDNIGHT) < (seconds.last - MIDDAY)! {|s| s < MIDDAY ? s += SECONDS_IN_DAY : s }
  end { |sum,n| sum += n }.to_f / seconds.length).strftime("%I:%M%p").downcase