min_hitting_set.py

def min_hitting_set(students):
	def help(students, tests):
		students = sorted(list(filter(lambda s: s and not (s & tests), students)), key=set.__len__)
		if students:
			student, *students = students
			return min(map(lambda t: help(students, set([t]) | tests), student), key=set.__len__)
		return tests

	return help(students, set())

if __name__ == '__main__':
	print(min_hitting_set(students))