Re: [SOLUTION] [QUIZ] 1-800-THE-QUIZ (#20)

On Mon, 21 Feb 2005 05:40:00 +0900
Brian Schrer <[e-mail]> wrote:

> Hello Group,
> 
> i once again found the time to do the ruby quiz. I liked the quiz
> because it was short, and on the other hand harder than I thought. I
> skipped the part about skipping letters in my first try, and when I had
> to add it it made me think quite a bit. (I first skipped letters instead
> of numbers, because I got confused in my datastructure.)
> 
> Now, heres my solution:
> 
> I build a tree index of the dictionary indexed by numbers and search
> this tree.
> 
> Thanks for the quiz James!
> 

Ooops, I didn't send the final version, and I did not include the link to my solution, so here is another try:

This version loads the dictionary a lot faster (3 times as fast as the old
version) because it does not create as many intermediate objects. Also I measured that upcasing and gsub'ing is faster on the long string than on the individual short strings.

Browse the solution online and in full color at:

http://ruby.brian-schroeder.de/quiz/phoneword/

or directly at

http://ruby.brian-schroeder.de/quiz/phoneword/browse/phoneword-rb.html

And to show it in all its glory (now loading the dictionary 3 times as fast:)


# Nodes in the Dictionary.
class DictionaryNode < Array
  # Terminal info
  attr_reader :words

  def initialize
    super()
    @words = []
  end
end

# A tree-indexed version of the dictionary that allows efficent searching by number 2 alphabet mapping.
class Dictionary
  def initialize(encoding)
    super()   
    @encoding = {}
    @inverse_encoding = {}

    encoding.each do | k, v |
      @encoding[k] = v.split(/\s+/).map{|c| c[0]}
    end

    # Create map from characters to numbers
    @inverse_encoding = @encoding.inject({}) { | r, (k, v) |
      v.each do | l | r[l] = k end
      r
    }
    @root = DictionaryNode.new
  end

  # Helper method for rekursive adding of words to the dictionary
  private
  def add_recursive(node, word, position)
    if word.length == position
      node.words << word
      return node
    end
    add_recursive(node[@inverse_encoding[word[position]]] ||= DictionaryNode.new, word, position + 1) 
  end

  # Add words to the dictionary
  public
  def add(word)
    add_recursive(@root, word, 0)
    self
  end
  
  # Load a wordlist from a file, which contains one word per line.
  # Ignores punctuation and whitespace.
  def load_wordlist(file)
    file.read.gsub!(/[^A-Za-z\n]/, '').upcase!.each do |w|
      w.chomp!
      next if w.empty?
      self.add(w)
    end
    self
  end

  private
  # Search words and return (in the block) words and the unmatched rest of the number
  def sub_find_noskip(node, number, &block)
    # Return words found so far
    block[node.words.map{|w|w.dup}, number] unless node.words.empty?
    # No more digits, so stop searching here
    return node if number.empty?
    # Search for longer words
    sub_find_noskip(node[number[0]], number[1..-1], &block) if node[number[0]]    
  end

  # Search words and return (in the block) words and the unmatched rest of the number.
  # Allows to skip parts of the words, returning the skipped positions as a binary array.
  def sub_find(node, number, skipped = [], &block)
    # Return words found so far
    block[node.words.map{|w|w.dup}, number, skipped] unless node.words.empty?
    # No more digits, so stop searching here
    return node if number.empty?
    # Search for longer words
    sub_find(node[number[0]], number[1..-1], skipped + [false], &block) if node[number[0]]    
    # If previous digit was not skipped, allow to skip this one
    sub_find(node, number[1..-1], skipped + [true], &block) if !skipped[-1]
  end

  public
  # Skipping makes this a bit ugly
  def find(number, options)
    result = []
    if options.allow_skips
      sub_find(@root, number) do | words, rest_number, skipped |
        # Interleave skipped numbers
        needle = []
        skipped.zip(number).each_with_index do |(s,n), i|
          needle << [n, i] if s
        end
        words.each do | w |
          needle.each do | (n, i) | w.insert(i, n.to_s) end
        end
        
        if rest_number.empty?
          result.concat(words)
        else
          find(rest_number, options).each do | sentence |
            words.each do | w |
              result << w + '-' + sentence
            end
          end
        end
      end
    else
      sub_find_noskip(@root, number) do | words, rest_number |
        if rest_number.empty?
          result.concat(words)
        else
          find(rest_number, options).each do | sentence |
            words.each do | w |
              result << w + '-' + sentence
            end
          end
        end
      end
    end
    result
  end 
end

encodings = {
  :james => {
    2 => 'A B C',
    3 => 'D E F',
    4 => 'G H I',
    5 => 'J K L',
    6 => 'M N O',
    7 => 'P Q R S',
    8 => 'T U V',
    9 => 'W X Y Z'},

  :logic => {
    0 => 'A B',
    1 => 'C D',
    2 => 'E F',
    3 => 'G H',
    4 => 'I J K',
    5 => 'L M N',
    6 => 'O P Q',
    7 => 'R S T',
    8 => 'U V W',
    9 => 'X Y Z'
  }
}

require 'optparse'

class PhonewordOptions < OptionParser
  attr_reader :dictionary, :encoding, :format, :allow_skips, :help, :encoding_help
  def initialize
    super()
    @dictionary = '/usr/share/dict/words'
    @encoding = :james
    @format = :plain
    @allow_skips = true
    @help = false
    @encoding_help = false
    self.on("-d", "--dictionary DICTIONARY", String) { | v | @dictionary = v }
    self.on("-e", "--encoding ENCODING", String,
            "How the alphabet is encoded to phonenumbers. james or logic are supported.") { | v | @encoding   = v.downcase.to_sym }
    self.on("-p", "--plain", 'One result per found number, no other information') { @format = :plain }
    self.on("-v", "--verbose", 'Prefix the result with the number')               { @format = :verbose }
    self.on("-s", "--skips", "--allow_skips", "--allow-skips", 'Allow to skip one adjacent number while matching. ',
            'Gives lots of ugly results, but james asked for it.')   { @allow_skips  = true }
    self.on("-c", "--no-skips", "Don't leave numbers in the detected words") { @allow_skips  = false }
    self.on("-?", "--help") { @help = true }
    self.on("--supported-encodings", "--encoding-help", "List the supported encodings") { @encoding_help = true }
  end
end

options = PhonewordOptions.new
options.parse!(ARGV)

if options.help
  puts options
  exit
end

if options.encoding_help or !encodings[options.encoding]
  puts "Possible encodings:"
  puts encodings.to_a.sort_by{|(k,v)|k.to_s}.map{|(k,v)| "#{k}:\n"+v.map{|(n,e)|"  #{n}: #{e}"}.sort.join("\n")}
  exit
end

dictionary = Dictionary.new(encodings[options.encoding]).load_wordlist(File.open(options.dictionary))

output = {
  :plain   => lambda do | number, sentence | sentence end,
  :verbose => lambda do | number, sentence | "#{number.ljust(15)}: #{sentence}" end }

ARGF.each do | number |
  number.strip!
  dictionary.find(number.gsub(/[^0-9]/, '').unpack('C*').map{|n|n - ?0}, options).each do | sentence |
    puts output[options.format][number, sentence]
  end
end