Embed.ly challenge

find_8001.rb

def check_number(n)
  n_f = 1.upto(n).inject(&:*)
  sum_of_digits = n_f.to_s.each_char.inject(0) do |res, v|
    res += v.to_i
  end
  [n_f, sum_of_digits]
end

found = false
i = 1
while not found do
  res = check_number(i)
  puts "Checking #{i}!, is #{res[0]}, sum of digits #{res[1]}"
  i += 1
  found = true if res[1] == 8001
end

std_dev.rb

require "open-uri"
require "nokogiri"

url = "http://apply.embed.ly/static/data/2.html"

doc = Nokogiri::HTML(open(url))

article = doc.css("article").first

def mark_depth(start, n)
  if start.name == "p" then
    res = n
  else
    res = nil
  end

  children = start.children.map do |child|
    mark_depth(child, n+1)
  end

  [res, children].flatten.compact
end

res = mark_depth(article, 1)

mean = res.inject(&:+) / res.count.to_f

deviations = res.map{|n| (n - mean) * (n - mean)}

deviations_avg = deviations.inject(&:+) / deviations.count.to_f

std_dev = Math.sqrt(deviations_avg)

puts std_dev

zipf.rb

require "pry"
nums = 1.upto(900)

multiplier = nums.inject(&:+)

frequencies = nums.each_with_index.map{|n, index| 
  multiplier / (index + 1)
}

all = frequencies.inject(&:+)

half = all / 2

frequencies.each_with_index.inject(0) do |result, (value, index)|
  result += value
  if result >= half
    puts index + 1
    break
  end
  result
end