calculate_minimum_hp_dungeon.rb

def calculate_minimum_hp(dungeon)
  state=[(2**32)] * (dungeon[0].size+1)
  state[dungeon[0].size-1] = 1  #if you set state[-1]=1,  error occurs in next new loop
  (dungeon.size-1).downto(0) do |i|
    (dungeon[0].size-1).downto(0) do |j|
      state[j]=[1, [state[j], state[j+1]].min-dungeon[i][j]].max
    end
  end
  state[0]
end
a=[[-2,-3,3],
   [-5,-10,1],
   [10,30,-5]]
p calculate_minimum_hp(a)