import aocd
import collections

def parse_rules(orders):
    """
    Return a dictionary mapping page numbers to lists of page numbers
    For any given key, each page of the value must come after it
    """
    rules = collections.defaultdict(list)

    for order in orders:
        k,v = order.split('|')
        rules[k].append(v)

    return rules

def verify_update(update, rules):
    """
    Ensure that an update is valid using an O(n^2) approach that will
    bite me in the ass in part B somehow
    """
    update = update.split(',')
    for n, page in enumerate(update):
        for prev_page in update[:n]:
            if prev_page in rules[page]:
                return 0
    return int(update[len(update)//2])


def solve(data):
    orders, updates = data.split('\n\n')
    rules = parse_rules(orders.split('\n'))
    return sum(verify_update(u, rules) for u in updates.split('\n'))

if __name__ == '__main__':
    puz = aocd.models.Puzzle(year=2024, day=5)

    # data = puz.examples[0].input_data
    data = puz.input_data

    solution = solve(data)

    print(solution)
    aocd.submit(solution, year=2024, day=5, part='a')