My solution was selected as the winning solution for RubyLearning.com’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} seconds.sort! if (seconds.first - MIDNIGHT) < (seconds.last - MIDDAY) seconds.map! {|s| s < MIDDAY ? s += SECONDS_IN_DAY : s } end Time.at(seconds.inject { |sum,n| sum += n }.to_f / seconds.length).strftime("%I:%M%p").downcase end

Gist: https://gist.github.com/5b371226faf83af50d7e

Interview: http://rubylearning.com/blog/2009/10/22/charles-feduke-winner-rpcfn-2/