day02.py

def parse_line(line):
    policy, password = line.split(": ")
    rule, target = policy.split(" ")
    a, b = [int(x) for x in rule.split("-")]

    return a, b, target, password


input = open("../input/day02.txt").read()
passwords = [parse_line(x) for x in input.splitlines()]


def validate_part_one(min, max, target, password):
    """
    Validate whether the given password contains the target character at least `min` times, and no more than `max`.
    """
    count = len([c for c in password if c == target])
    return count >= min and count <= max


def validate_part_two(a, b, target, password):
    """
    Validate whether the given password contains the target character in position `a` or `b`, but not both.
    """
    return (password[a - 1] == target) ^ (password[b - 1] == target)


print("part one: %d" % len([p for p in passwords if validate_part_one(*p)]))
print("part two: %d" % len([p for p in passwords if validate_part_two(*p)]))