プロジェクトオイラー17

sample.rb

# http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2017
base_one = ["one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
base_ten = ["ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]
base_hundred = "hundred"
base_thousand = "thousand"
exceptions = ["eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]

base =  base_one + base_ten + exceptions + base_ten.slice(1..-1).product(base_one).map { |set| set[0] ++ set[1] }
punctuation =  base_one.map{ |b| b + base_hundred }
middle = base +  punctuation.product(base).map { |set| set[0] + "and"+ set[1] }
puts middle.map { |m| m.length }.inject(:+) + punctuation.map{ |m| m.length }.inject(:+) + ("one" + base_thousand).length