Advent of Code 2020 Day 21

AoC2020_day21.py

from functools import reduce

import re

def get_allergens(input):
    ingredient_list = []
    allergen_map = {}

    for line in input:
        m = re.match("^([\w\s]+) \(contains ([\w\s,]+)\)$", line).groups()

        ingredients = m[0].split(" ")
        allergens = m[1].split(", ")

        for allergen in allergens:
            if allergen not in allergen_map:
                allergen_map[allergen] = set(ingredients)
            else:
                allergen_map[allergen] &= set(ingredients)

        ingredient_list.extend(ingredients)

    safe_ingredients = set(ingredient_list) - reduce(lambda a, b: a.union(b), allergen_map.values())
    result_p1 = sum([ingredient_list.count(i) for i in safe_ingredients])

    unique_allergen_map = {}
    while max([len(v) for v in allergen_map.values()]) > 0:
        for k, v in allergen_map.items():
            if len(v) == 1:
                unique_allergen_map[k] = v.pop()
        for k in allergen_map:
            allergen_map[k] -= set(unique_allergen_map.values())

    result_p2 = ','.join([v for k, v in
                            sorted([(k, v) for k, v in
                                unique_allergen_map.items()])])

    return result_p1, result_p2

with open("input_21") as fp:
    print(get_allergens(fp))