格子状のマップを上下左右に動いてゴールを目指すプログラム

explore.rb

def create_field(str)
  str = str.gsub(/\A\n+|\n+\z/, "")
  str.split("\n").map{ |line| line.split(//) }
end

def find_start_goal(field)
  result = {}
  field.each_with_index do |line, i|
    line.each_with_index do |cell, j|
      if cell == "S" || cell == "G"
        result[cell] = [i, j]
      end
    end
  end
  result
end

def main(field, prob_goal_direction)
  start, goal = find_start_goal(field).values_at("S", "G")
  pos = start

  # 探索
  i = 0
  until pos == goal
    i += 1
    direction = [0, 0]
    
    if rand() < prob_goal_direction
      # ゴールのある向きへ向かう。確率は距離で決定
      x_distance_to_goal = goal[0] - pos[0]
      y_distance_to_goal = goal[1] - pos[1]
      if rand(x_distance_to_goal.abs + y_distance_to_goal.abs) < x_distance_to_goal.abs
        direction = [pos[0] > 0 ? 1 : -1, 0]
      else
        direction = [0, pos[1] > 0 ? 1 : -1]
      end
    else
      # ランダムに動く。
      case rand(4)
      when 0
        direction = [1, 0]
      when 1
        direction = [-1, 0]
      when 2
        direction = [0, 1]
      when 3
        direction = [0, -1]
      end
    end
    
    pos_temp = [pos[0] + direction[0], pos[1] + direction[1]]
    redo if field[pos_temp[0]][pos_temp[1]] == "@"
    
    #puts "Step #{i}: #{pos.inspect} -> #{pos_temp.inspect}"
    pos = pos_temp
  end
  puts "Probability_of_going_for_goal,#{prob_goal_direction},Steps,#{i}"
end

if $0 == __FILE__
  # マップ定義
  field = create_field <<MAP
@@@@@@@@@
@S      @
@       @
@@@ @@@ @
@   @   @
@  @ G  @
@  @  @ @
@       @
@@@@@@@@@
MAP
  
  # コマンドライン引数には、確率（0から1の間）を与える。
  # その確率でゴールのある向きへ向かい、それ以外はランダムに進む。
  prob = Float(ARGV[0])
  main(field, prob)
end