どう書く# 23　http://nabetani.sakura.ne.jp/hena/ord23snakemoinc/

snake.rb

require 'minitest/unit'
require 'minitest/autorun'
require 'pry'

MAX_WIDTH  = 5
MAX_HEIGHT = 5

def solve(str)
  init_numbers_field(str)
  checked_field = init_checked_field

  count_length = []

  MAX_WIDTH.times do |x|
    MAX_HEIGHT.times do |y|
      pos = check_rise_up_number(x, y, [], checked_field)
      count_length << pos.size
    end
  end

  count_length.max
end

def init_numbers_field(str)
  @numbers_field = str.split('/').map(&:chars).transpose
end

def init_checked_field
  checked_field = Array.new
  MAX_WIDTH.times do
    checked_field << Array.new(MAX_HEIGHT, false)
  end
  checked_field
end

def check_rise_up_number(x, y, pos, checked_field)
  return pos if checked_field[x][y] == true

  pos << [x, y]
  checked_field[x][y] = true
  current_number = @numbers_field[x][y].to_i

  if (y > 0) and (@numbers_field[x][y-1].to_i > current_number) and !(checked_field[x][y-1])
    check_rise_up_number(x, y-1, pos, checked_field)
  end

  if (x < MAX_WIDTH - 1) and (@numbers_field[x+1][y].to_i > current_number) and !(checked_field[x+1][y])
    check_rise_up_number(x+1, y, pos, checked_field)
  end

  if (x > 0) and (@numbers_field[x-1][y].to_i > current_number) and !(checked_field[x-1][y])
    check_rise_up_number(x-1, y, pos, checked_field)
  end

  if (y < MAX_HEIGHT - 1) and (@numbers_field[x][y+1].to_i > current_number) and !(checked_field[x][y+1])
    check_rise_up_number(x, y+1, pos, checked_field)
  end

  pos
end

class TestFoo < MiniTest::Unit::TestCase
  def test_exercise_no1
    assert_equal(solve('01224/82925/69076/32298/21065'), 6)
  end
end