Restyled README and file structure

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

2020/solutions/day_21.py

@@ -0,0 +1,110 @@
+"""AOC 2020 Day 21"""
+
+import pathlib
+import time
+import collections
+
+TEST_INPUT = """mxmxvkd kfcds sqjhc nhms (contains dairy, fish)
+trh fvjkl sbzzf mxmxvkd (contains dairy)
+sqjhc fvjkl (contains soy)
+sqjhc mxmxvkd sbzzf (contains fish)"""
+
+def read_input(input_path: str) -> str:
+    """take input file path and return a str with the file's content"""
+    with open(input_path, 'r') as input_file:
+        input_data = input_file.read().strip()
+        return input_data
+
+def extract(input_data: str) -> tuple:
+    """take input data and return the appropriate data structure"""
+    recipes = list()
+    ingredient_allergenes = collections.defaultdict(set)
+    recipes_with_allergene = collections.defaultdict(list)
+
+    for index, recipe in enumerate(input_data.split('\n')):
+        ingredients, allergenes = recipe.split(' (contains ')
+        ingredients = set(ingredients.split())
+        allergenes = set(allergenes.rstrip(')').split(', '))
+
+        recipes.append(ingredients)
+        for ingredient in ingredients:
+            ingredient_allergenes[ingredient] |= allergenes
+        for allergene in allergenes:
+            recipes_with_allergene[allergene].append(index)
+
+    return recipes, ingredient_allergenes, recipes_with_allergene
+
+def find_safe_ingredients(recipes: list, ingredient_allergenes: dict, recipes_with_allergene: dict) -> list:
+    """return a list of ingredients not containing allergenes"""
+    safe_ingredients = list()
+    for ingredient, allergenes in ingredient_allergenes.items():
+        impossible_allergenes = set()
+        for allergene in allergenes:
+            if any(ingredient not in recipes[i] for i in recipes_with_allergene[allergene]):
+                impossible_allergenes.add(allergene)
+        allergenes -= impossible_allergenes
+        if not allergenes:
+            safe_ingredients.append(ingredient)
+    return safe_ingredients
+
+def assign_allergenes(ingredient_allergenes: dict) -> dict:
+    """return a dict with each ingredient and its allergene"""
+    assigned_allergenes = dict()
+    while ingredient_allergenes:
+        assigned_allergene = str()
+        assigned_ingredient = str()
+
+        for ingredient, allergenes in ingredient_allergenes.items():
+            if len(allergenes) == 1:
+                assigned_allergene = allergenes.pop()
+                assigned_ingredient = ingredient
+                break
+        assigned_allergenes[assigned_allergene] = assigned_ingredient
+        ingredient_allergenes.pop(assigned_ingredient)
+
+        for ingredient, allergenes in ingredient_allergenes.items():
+            if assigned_allergene in allergenes:
+                allergenes.remove(assigned_allergene)
+
+    return assigned_allergenes
+
+def part1(entries: tuple) -> int:
+    """part1 solver"""
+    recipes, ingredient_allergenes, recipes_with_allergene = entries
+    safe_ingredients = find_safe_ingredients(recipes, ingredient_allergenes, recipes_with_allergene)
+
+    return sum(ingredient in recipe for recipe in recipes for ingredient in safe_ingredients)
+
+def part2(entries: tuple) -> str:
+    """part2 solver"""
+    recipes, ingredient_allergenes, recipes_with_allergene = entries
+    safe_ingredients = find_safe_ingredients(recipes, ingredient_allergenes, recipes_with_allergene)
+    for ingredient in safe_ingredients:
+        ingredient_allergenes.pop(ingredient)
+    assigned_allergenes = assign_allergenes(ingredient_allergenes)
+
+    return ','.join(map(assigned_allergenes.get, sorted(assigned_allergenes)))
+
+def test_input_day_21():
+    """pytest testing function"""
+    entries = extract(TEST_INPUT)
+    assert part1(entries) == 5
+    assert part2(entries) == 'mxmxvkd,sqjhc,fvjkl'
+
+def test_bench_day_21(benchmark):
+    """pytest-benchmark function"""
+    benchmark(main)
+
+def main():
+    """main function"""
+    input_path = str(pathlib.Path(__file__).resolve().parent.parent) + "/inputs/" + str(pathlib.Path(__file__).stem)
+    start_time = time.time()
+    input_data = read_input(input_path)
+    entries = extract(input_data)
+    print("Part 1: %d" % part1(entries))
+    print("Part 2: %s" % part2(entries))
+    end_time = time.time()
+    print("Execution time: %f" % (end_time-start_time))
+
+if __name__ == "__main__":
+    main()