all_topo.rb

topo.rb

# 位相空間を全て数え上げるプログラム

def dedup(arr)
  arr.map {|c| c.sort}.uniq.sort_by {|x| x.length}
end
def topo(xs)
  return [[]] if xs.empty?
  rest = topo(xs[1..])
  dedup(rest.flat_map {|c| [c & xs[0], c | xs[0], c]})

end
def combs(xs)
  return [[]] if xs.empty?
  rest = combs(xs[1..])
  rest.map { |c| [xs[0]] + c } + rest
end
def all_topo(xs)
  dedup(combs(combs(xs)).map {|comb| topo([*[[], xs], *comb])})
end

p all_topo([1,2,3,4]).length