kame.rb

# -*- encoding: utf-8 -*-
require 'pp'

class Edge
  attr_accessor :sides
  def initialize(a, b)
    @sides = [a, b]
  end

  def inspect
    "Edge#{sides.inspect}"
  end

  def another_side(input)
    sides = @sides.dup
    sides.delete(input)
    return sides[0] if sides.size == 1
    raise "Unknown side #{input.inspect} for #{sides.inspect}"
  end
end

class Cursor
  attr_accessor :pos, :vector, :history

  def initialize
    @pos = 'A'
    @history = [@pos]
    @vector = 'r'
  end

  def exec!(command)
    return unless @pos

    case command
    when 'L'
      turn_left!
    when 'R'
      turn_right!
    when /[0-9a-f]/
      walk!(command.to_i(16))
    end
  end

  def turn_left!
    table = {
      't' => 'l',
      'l' => 'b',
      'b' => 'r',
      'r' => 't',
    }
    @vector = table[@vector]
  end

  def turn_right!
    table = {
      't' => 'r',
      'l' => 't',
      'b' => 'l',
      'r' => 'b',
    }
    @vector = table[@vector]
  end

  def walk!(n)
    return if n == 0

    edge = $edge_hash[@pos + @vector]
    unless edge
      @history << '?'
      @pos = nil
      return
    end

    another_side = edge.another_side(@pos + @vector)
    next_pos, entry_vector = another_side.split(//)
    @pos = next_pos
    @vector = reverse_side(entry_vector)
    @history << @pos
    walk!(n - 1)
  end

  def reverse_side(v)
    table = {
      't' => 'b',
      'l' => 'r',
      'b' => 't',
      'r' => 'l',
    }
    table[v]
  end

  def result
    @history.join
  end
end

$data = <<EOS
ABCDEFGHIJK
LMNOPQRSTUV
WXYZabcdefg
hij
klm
nop
qrs
tuv
wxy
z01
234
567
EOS

$edges = []
$edge_hash = {}

def transpose_force(matrix)
  max_len = matrix.map(&:size).max
  result = []
  (0...max_len).each {|i|
    result << matrix.map {|l| l[i]}
  }
  result

end

def build_matrix
  matrix = []
  $data.split(/\n/).each {|line|
    matrix << line.chomp.split(//)
  }
  matrix.each {|line|
    line.each_cons(2) {|left, right|
      $edges << Edge.new(left + 'r', right + 'l')
    }
  }

  transpose_force(matrix).each {|col|
    col.each_cons(2) {|top, bottom|
      if top && bottom
        $edges << Edge.new(top + 'b', bottom + 't')
      end
    }
  }

  $edges << Edge.new('5b', 'gb')
  $edges << Edge.new('6b', 'fb')
  $edges << Edge.new('7b', 'eb')

  $edges.each {|e|
    e.sides.each {|s|
      $edge_hash[s] = e
    }
  }
end

build_matrix

def test(commands, expect)
  cursor = Cursor.new
  commands.split(//).each {|command|
    cursor.exec!(command)
  }
  p([cursor.result == expect, cursor.result, expect])
end

def main
  test( "2RcL3LL22", "ABCNYjmpsvy147edcbcdef" )
  test( "L3R4L5RR5R3L5", "A?" )
  test( "2ReLLe", "ABCNYjmpsvy147eTITe741yvspmjYNC" )
  test( "1ReRRe", "ABMXilorux036fUJUf630xuroliXMB" )
  test( "ReRRe", "ALWhknqtwz25gVKVg52zwtqnkhWLA" )
  test( "f", "ABCDEFGHIJK?" )
  test( "Rf", "ALWhknqtwz25gVK?" )
  test( "1Rf", "ABMXilorux036fUJ?" )
  test( "2Rf", "ABCNYjmpsvy147eTI?" )
  test( "aR1RaL1LaR1R2L1L2", "ABCDEFGHIJKVUTSRQPONMLWXYZabcdefg567432" )
  test( "2R1R2L1L2R1R2L1L2R1R2L1L2R1R2L1L2", "ABCNMLWXYjihklmponqrsvutwxy" )
  test( "2R4R2L4L2R4R2L4L2R4R2L4L2", "ABCNYjmlknqtwxy147efgVK?" )
  test( "R1L2R4R2L4L2R4R2L4L2R4R2L4L2", "ALMNYjmponqtwz0147eTUVK?" )
  test( "R2L2R4R2L4L2R4R2L4L2R4R2L4L2", "ALWXYjmpsrqtwz2347eTIJK?" )
  test( "R3L2R4R2L4L2R4R2L4L2R4R2L4L2", "ALWhijmpsvutwz2567eTI?" )
  test( "R5L2L5L1LaR1L4L5", "ALWhknopmjYNCBMXilorux0325gVKJIHGF" )
  test( "1R2L4L2R4R2L4L2R4", "ABMXYZabQFGHIJUfg?" )
  test( "2R2L4L2R4R2L4L2R4", "ABCNYZabcRGHIJKVg?" )
  test( "3R2L4L2R4R2L4L2R4", "ABCDOZabcdSHIJK?" )
  test( "4R2L4L2R4R2L4L2R4", "ABCDEPabcdeTIJK?" )
  test( "5R2L4L2R4R2L4L2R4", "ABCDEFQbcdefUJK?" )
  test( "LLL1RRR1LLL1RRR2R1", "ALMXYZ?" )
  test( "R3RRR3", "ALWhij?" )
  test( "1LLL4RRR1LR1RL1", "ABMXilm?" )
  test( "R2L1R2L1R3R4", "ALWXilmpsvut?" )
  test( "7R4f47LLLc6R9L", "ABCDEFGHSd?" )
  test( "5RR868L8448LL4R6", "ABCDEFEDCBA?" )
  test( "42Rd1RLLa7L5", "ABCDEFGRc?" )
  test( "RRLL6RLR1L5d12LaLRRL529L", "ABCDEFGRSTUV?" )
  test( "RLR7L6LL1LRRRcRL52R", "ALWhknqtuv?" )
  test( "1RLR8RLR1R437L99636R", "ABMXiloruxwtqnkhWLA?" )
  test( "LLL2L3La9Le5LRR", "ALWXYZOD?" )
  test( "R1LcRR491", "ALMNOPQRSTUV?" )
  test( "R8L1R1R512L8RLLReRf", "ALWhknqtwx0z?" )
  test( "1RcL8f1L29a5", "ABMXilorux036fedcbaZYXW?" )
  test( "R822LeL46LL39LL", "ALWhknqtwz25gfedcbaZYXW?" )
  test( "9R3L5LRRLb5R3L7cLLLR4L", "ABCDEFGHIJUf65?" )
  test( "7LLRRR2R3R69Lf76eR2L", "ABCDEFGHSdcbaPE?" )
  test( "8RRRLL3Le", "ABCDEFGHITe765?" )
  test( "8R5RLL6LbL4LL5bL", "ABCDEFGHITe7410z?" )
  test( "6LR2R1LR5LRLRL484L63", "ABCDEFGHITe741yxw?" )
end

case $0
when __FILE__
  main
when /spec[^\/]*$/
  # {spec of the implementation}
end