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

snakemoinc.rb

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

MAX_WIDTH  = 5
MAX_HEIGHT = 5
SENTINEL_CHER = -1

def solve(str)
  init_numbers_field(str)
  init_memo

  count_depthes = []

  MAX_WIDTH.times do |x|
    MAX_HEIGHT.times do |y|
      count_depthes << count_depth(x + 1, y + 1)
    end
  end

  count_depthes.max
end

# 入力値を二次元配列にする
def init_numbers_field(str)
  @numbers_field = str.split('/').map(&:chars).transpose
  @numbers_field.each { |row| row.map!(&:to_i) }

  # 番兵
  horizontal_sentinels = Array.new(MAX_WIDTH, SENTINEL_CHER)
  @numbers_field.push horizontal_sentinels
  @numbers_field.unshift horizontal_sentinels
  @numbers_field.map do |row|
    row.push SENTINEL_CHER
    row.unshift SENTINEL_CHER
  end
end

# メモ化用の二次元配列を作る
def init_memo
  @max_depth_memo = []

  # 番兵を配慮して、MAX_WIDTH と MAX_HEIGHT に +2 する
  (MAX_WIDTH + 2).times do
    @max_depth_memo << Array.new(MAX_HEIGHT + 2, nil)
  end
end

def count_depth(x, y)
  return 0 if @numbers_field[x][y] == SENTINEL_CHER
  return @max_depth_memo[x][y] if @max_depth_memo[x][y]

  count_depthes = [1]
  current_number = @numbers_field[x][y]

  if @numbers_field[x][y - 1] > current_number
    count_depthes << (1 + count_depth(x, y - 1))
  end

  if @numbers_field[x + 1][y] > current_number
    count_depthes << (1 + count_depth(x + 1, y))
  end

  if @numbers_field[x - 1][y] > current_number
    count_depthes << (1 + count_depth(x - 1, y))
  end

  if @numbers_field[x][y + 1] > current_number
    count_depthes << (1 + count_depth(x, y + 1))
  end

  # メモ化
  @max_depth_memo[x][y] = count_depthes.max

  @max_depth_memo[x][y]
end

class TestFoo < MiniTest::Unit::TestCase
  SAMPLES = [
    ['01224/82925/69076/32298/21065', 6],
    ['03478/12569/03478/12569/03478', 10],
    ['09900/28127/87036/76545/87650', 10],
    ['77777/77777/77777/77777/77777', 1],
    ['00000/11111/22222/33333/44444', 5],
    ['01234/12345/23456/34567/45678', 9],
    ['10135/21245/43456/55567/77789', 8],
    ['33333/33333/55555/55555/77777', 2],
    ['01234/11234/22234/33334/44444', 5],
    ['98765/88765/77765/66665/55555', 5],
    ['01234/10325/23016/32107/45670', 8],
    ['34343/43434/34343/43434/34343', 2]
  ]

  SAMPLES.each_with_index do |sample_data, idx|
    define_method "test_exercise_no#{idx}" do
      assert_equal(solve(sample_data.first), sample_data.last)
    end
  end
end