Embedly Programming Challenge

emberly.rb

#!/usr/bin/env ruby -w

#------------------------------------------------------------------------------
# requires
#------------------------------------------------------------------------------

require 'open-uri'

#------------------------------------------------------------------------------
# Problem #1
#------------------------------------------------------------------------------

def problem_1
    ((0..1000).map{ |x| { :d => x, :v => (((1..x).inject:*).to_s.split('').map{ |d| d.to_i }.inject:+) } }).find_all{ |h| (h[:v] == 8001) }[0][:d]
end
 
#------------------------------------------------------------------------------
# Problem #2
#------------------------------------------------------------------------------

# Note: standard deviation code copied from:
#  https://www.bcg.wisc.edu/webteam/support/ruby/standard_deviation

#  Add methods to Enumerable, which makes them available to Array
module Enumerable
 
  #  sum of an array of numbers
  def sum 
    return self.inject(0){|acc,i|acc+i}
  end 
 
  #  average of an array of numbers
  def average
    return self.sum/self.length.to_f
  end 
 
  #  variance of an array of numbers
  def sample_variance
    avg=self.average
    sum=self.inject(0){|acc,i|acc+(i-avg)**2}
    return(1/self.length.to_f*sum)
  end 
 
  #  standard deviation of an array of numbers
  def standard_deviation
    return Math.sqrt(self.sample_variance)
  end 
 
end  #  module Enumerable

#------------------------------------------------------------------------------

def problem_2
    open('http://apply.embed.ly/static/data/2.html'){ |f| f.read }.split("\n").grep(/(<article>|<\/article>|<div>|<\/div>|<p>)/).inject({:i=>0, :l=>[]}) { |h,x| h[:i] += x =~ /(<article>|<div>)/ ? 1 : x =~ /(<\/article>|<\/div>)/ ? -1 : 0; h[:l] += [h[:i]] if x =~ /<p>/; h }[:l].standard_deviation
end

#------------------------------------------------------------------------------
# Problem #3
#------------------------------------------------------------------------------

def problem_3
    ([900*900]*900).zip(1..900).map{ |x| x[0]/x[1] }.inject([[0, 0]]){ |l,v| l += [[v,l[-1][1]+v]] }.reject{ |x| x[1] > 2988774 }.count
end

#------------------------------------------------------------------------------
# main
#------------------------------------------------------------------------------

puts "Problem #1: #{problem_1}"
puts "Problem #2: #{problem_2}"
puts "Problem #3: #{problem_3}"