2020/21

y2020/p21.py

@@ -0,0 +1,54 @@
+import sys
+
+
+text = sys.stdin.read()
+test = '''mxmxvkd kfcds sqjhc nhms (contains dairy, fish)
+trh fvjkl sbzzf mxmxvkd (contains dairy)
+sqjhc fvjkl (contains soy)
+sqjhc mxmxvkd sbzzf (contains fish)'''
+
+
+contains = {}
+for line in text.splitlines():
+    food, allergens = line[:-1].split(' (contains ')
+    food = frozenset(s.strip() for s in food.split(' '))
+    allergens = frozenset(s.strip() for s in allergens.split(','))
+    contains[food] = allergens
+
+all_allergens = {a for b in contains.values() for a in b}
+all_foods = {a for b in contains.keys() for a in b}
+
+reverse = {}
+for food in all_foods:
+    reverse[food] = set(all_allergens)
+
+for food, allergens in contains.items():
+    for f2 in reverse:
+        if f2 not in food:
+            reverse[f2] -= allergens
+
+clean = {k for k, v in reverse.items() if not v}
+ans = 0
+for v in contains.keys():
+    ans += len(v & clean)
+print(ans)
+
+
+final = {v: k - clean for k, v in contains.items()}
+
+
+def recurse(ings, known=tuple()):
+    if not ings:
+        yield known
+    else:
+        key, = min(ings, key=lambda k: len(k))
+        for val in sorted(ings.pop(frozenset({key}))):
+            expa = known + ((key, val),)
+            lob = {k - {key}: v - {val} for k, v in ings.items()}
+            yield from recurse(lob, expa)
+
+
+for out in recurse(dict(final)):
+    d = dict(out)
+    if all(({d[e] for e in k} <= set(v)) for k, v in final.items()):
+        print(','.join(v for _, v in sorted(out)))