hangman.rb

require 'json'
require_relative 'hangman/game'

module Hangman
  UNKNOWN_LETTER = '*'
  class << self
    private
      def build_tree(chars, words, belongs_to_key)
        # No more guess needed if key doesn't contain any unknown letter
        unless belongs_to_key.include? UNKNOWN_LETTER
          return {}
        end

        # 从可能单词中选出猜中几率最大的字母
        optimal_c = chars.max_by do |char|
          words.count { |word| word.include? char }
        end
        chars -= [optimal_c] # Do NOT ues Array#delete


        reg = Regexp.new("[#{chars.join}]")
        tree = words.group_by { |word| word.gsub reg, UNKNOWN_LETTER }

        # build sub tree
        tree.each do |key, value|
          tree[key] = build_tree chars, value, key
        end

        # Return optimal solution and sub tree
        {
          :c => optimal_c,
          :t => tree
        }
      end
  end

  def self.build_decision_tree(word_list_file)
    words = File.read("./data/en.txt").upcase.strip.split
    tree = words.group_by do |word|
      '*' * word.size
    end
    tree.each do |key, value|
      tree[key] = build_tree ('A'..'Z').to_a, value, key
    end
  end

  def self.play(game)
    game.play
  end
end