Solves 538 Riddler Express for Feb 22 2019

538_liar_ages.py

statements = [
  ('a', 'b', lambda x: x > 20),
  ('b', 'c', lambda x: x > 18),
  ('c', 'd', lambda x: x < 22),
  ('d', 'e', lambda x: x != 17),
  ('e', 'a', lambda x: x > 21),
  ('a', 'd', lambda x: x > 16),
  ('b', 'e', lambda x: x < 20),
  ('c', 'a', lambda x: x == 19),
  ('d', 'b', lambda x: x == 20),
  ('e', 'c', lambda x: x < 18)
]

def check(ages):
    for (speaker, subject, age_test) in statements:
        if speaker in ages and subject in ages:
            if (ages[speaker] >= l) == age_test(ages[subject]):
                return False
    return True

def search_ages(ages, unassigned):
    if check(ages):
        if len(unassigned) == 0:
            print 'found solution, l={}, ages={}'.format(l, ages)
        else:
            for a in range(16, 23):
                ages[unassigned[0]] = a
                search_ages(ages, unassigned[1:])
                del ages[unassigned[0]]

for l in range(16, 23):
    search_ages({}, ['a', 'b', 'c', 'd', 'e'])