popular_toppings.rb

require 'httparty'
require 'json'

=begin
Using any modern language, write a throw-away app or script that will download orders directly from http://files.olo.com/pizzas.json and output the top 20 most frequently ordered pizza topping combinations. List the toppings for each popular pizza topping combination along with its rank and the number of times that combination has been ordered.
=end

res = HTTParty.get('http://files.olo.com/pizzas.json')
data = JSON.parse(res)

def tally_data(data)
  tally = Hash.new
  data.each do |record|
    record['toppings'].each do |tp|
      unless tally.has_key? tp
        tally.store(tp, 1)
      else
        new_total = tally[tp] + 1 
        tally.store(tp, new_total)
      end
    end
  end
  return tally
end

def rank_toppings(hash)
  rankings = Array.new
  hash.each_pair do |topping, orders|
    if rankings.length == 0 
      rankings << [topping, orders]
    else
      rankings.each_with_index do |record, ii|
        if record.last < orders
          rankings.insert(ii, [topping, orders])
          break
        elsif ii + 1 == rankings.length
          rankings << [topping, orders]
          break
        end
      end
    end
  end
  return rankings
end

result =  rank_toppings(tally_data(data))[0..19]

puts
result.each_with_index {|record,ii| puts "#{record.first} | rank: #{ii + 1} | orders: #{record.last} "}



# --------------------------------------------------------------------------------------
# REFACTOR AFTER STUDYING sorting algorithms !
# I haven't worked on a lot of sorting problems in my career, but I knew my first
# iteration was primitive. Here's another attempt after studying quicksort and the like.
# Not necessarily the most optimal, but better, and straightforward at least in my mind.

require 'httparty'
require 'json'


def tally_toppings(data)
  tally = Hash.new
  data.each do |record|
    toppings = record['toppings']
    toppings.each do |tp|
      unless tally.has_key? tp
        tally.store(tp, 1)
      else
        new_total = tally[tp] + 1
        tally.store(tp, new_total)
      end
    end
  end
  return tally
end

def filter_left_right(array, side=:left, offset=0)
  comparator = array.first
  comparator_count = comparator.last

  left_side, right_side = Array.new, Array.new

  for index in 1..array.length-1 do
    target = array[index]
    if target.last <= comparator_count
      left_side.append(target)
    elsif target.last > comparator_count
      right_side.append(target)
    end
  end

  comparator_index = offset + left_side.length
  right_offset = offset + left_side.length + 1

  @final[comparator_index] = comparator

  if left_side.length >= 3
    filter_left_right(left_side, :left, offset)
  elsif left_side.length == 2
    if left_side.first.last > left_side.last.last
      @final[offset], @final[offset + 1] = left_side.last, left_side.first
    else
      @final[offset], @final[offset + 1] = left_side.first, left_side.last
    end
  elsif left_side.length == 1
    @final[offset] = left_side.first
  end

  if right_side.length >= 3
    filter_left_right(right_side, :right, right_offset)
  elsif right_side.length == 2
    if right_side.first.last > right_side.last.last
      @final[right_offset], @final[right_offset + 1] = right_side.last, right_side.first
    else
      @final[right_offset], @final[right_offset + 1] = right_side.first, right_side.last
    end
  elsif right_side.length == 1
    @final[right_offset] = right_side.first
  end
end

def init_final_array(toppings_hash)
  arr = Array.new
  toppings_hash.length.times { arr << nil }
  return arr
end

res = HTTParty.get('http://files.olo.com/pizzas.json')
data = JSON.parse(res)

@toppings_data = tally_toppings(data)
@final = init_final_array(@toppings_data)

unsorted_array = @toppings_data.to_a
filter_left_right(unsorted_array)

for ii in 0..19 do
  topping = @final[@final.length - ii - 1]
  rank = ii + 1
  puts "#{topping.first} | rank: #{rank} count: #{topping.last}"
end

refactor output :

pepperoni | rank: 1 count: 6335
four cheese | rank: 2 count: 1611
mozzarella cheese | rank: 3 count: 1461
bacon | rank: 4 count: 1447
beef | rank: 5 count: 1140
sausage | rank: 6 count: 831
mushrooms | rank: 7 count: 733
italian sausage | rank: 8 count: 672
black olives | rank: 9 count: 456
chicken | rank: 10 count: 401
pineapple | rank: 11 count: 360
ham | rank: 12 count: 341
jalapenos | rank: 13 count: 258
green peppers | rank: 14 count: 206
canadian bacon | rank: 15 count: 174
diced white onions | rank: 16 count: 168
cheddar cheese | rank: 17 count: 154
diced tomatoes | rank: 18 count: 128
alredo sauce | rank: 19 count: 127
onions | rank: 20 count: 121