Advent of Code Day 16

"""Day 16 of Advent of Code 2020 Solution"""

from itertools import chain
import re


def ticket_io(file_location):
    with open(file_location, "r") as f:
        data = f.read().split("\n\n")

    fields = {}
    for row in data[0].split("\n"):
        row = row.split(":")
        row_name = row[0]

        pattern = r"(\d+-\d+)"
        v_pairs = []
        for l_h in re.findall(pattern, row[1]):
            low, high = l_h.split("-")
            low, high = int(low), int(high)
            v_pairs.append((low, high))
        fields[row_name] = v_pairs

    my_ticket = [int(i) for i in data[1].split("\n")[1].split(",")]

    nearby_tickets = []
    for ticket in data[2].split("\n")[1:]:
        nearby_tickets.append([int(i) for i in ticket.split(",")])

    return {"fields": fields, "my_ticket": my_ticket, "nearby_tickets": nearby_tickets}


def validate_tickets(ticket_info) -> list[list[int]]:
    validated_nearby_tickets = []
    field_ranges = [*chain.from_iterable(ticket_info["fields"].values())]
    for ticket in ticket_info["nearby_tickets"]:
        ticket_val_bool = [False] * len(ticket)
        for i, val in enumerate(ticket):
            field_range_bool = [False] * len(field_ranges)
            for j, r in enumerate(field_ranges):
                if r[0] <= val <= r[1]:
                    field_range_bool[j] = True
            if any(field_range_bool):
                ticket_val_bool[i] = True
        if all(ticket_val_bool):
            validated_nearby_tickets.append(ticket)
    return validated_nearby_tickets


def part_a(file_location):
    pattern = r"(\d+-\d+)"
    with open(file_location, "r") as f:
        data = f.read().split("\n\n")
    v_pairs = []
    for v in data[0].split("\n"):
        for l_h in re.findall(pattern, v):
            low, high = l_h.split("-")
            low, high = int(low), int(high)
            v_pairs.append((low, high))

    error_rate = 0
    for ticket in data[2].split("\n")[1:]:
        for val in [int(i) for i in ticket.strip().split(",")]:
            found = [False] * len(v_pairs)
            for i, pair in enumerate(v_pairs):
                if pair[0] <= val <= pair[1]:
                    found[i] = True
            if not any(found):
                error_rate += val
    return error_rate


def value_in_field(field, val) -> bool:
    val_bool = [False] * len(val)
    for i, val in enumerate(val):
        field_bool = [False] * len(field)
        for j, field_range in enumerate(field):
            if field_range[0] <= val <= field_range[1]:
                field_bool[j] = True
        if any(field_bool):
            val_bool[i] = True
    return all(val_bool)


def part_b(file_location):
    ticket_info = ticket_io(file_location)
    valid_tickets = validate_tickets(ticket_info)
    ticket_len = len(valid_tickets[0])
    field_position = {field: [] for field in ticket_info["fields"].keys()}
    available_fields = {*ticket_info["fields"].keys()}
    found_positions = set()
    while available_fields:
        for position in range(ticket_len):
            if position not in found_positions:
                ticket_position_vals = [v[position] for v in valid_tickets]
                for field in available_fields:
                    if value_in_field(
                        ticket_info["fields"][field], ticket_position_vals
                    ):
                        field_position[field].append(position)
        for field in field_position:
            if field in available_fields:
                if len(field_position[field]) == 1:
                    available_fields.remove(field)
                    found_positions.add(field_position[field][0])
                else:
                    field_position[field] = []

    departure_fields = [field for field in field_position if field[:9] == "departure"]
    output = 1
    for field in departure_fields:
        output *= ticket_info["my_ticket"][field_position[field][0]]

    return output


if __name__ == "__main__":
    file_location = r"data\day16.txt"
    print(part_a(file_location))
    print(part_b(file_location))