1 files changed, 36 insertions, 0 deletions
diff --git a/20/py/d21.py b/20/py/d21.py
new file mode 100644
index 0000000..9f08b8c
--- /dev/null
+++ b/20/py/d21.py
@@ -0,0 +1,36 @@
+import aoc20
+import sys
+import itertools
+from collections import defaultdict
+
+
+def ingredients(line):
+    return line[:line.find(" (")].split(" ")
+
+
+def allergens(line):
+    return line[line.find(" (contains ")+len(" (contains "):-2].split(", ")
+
+
+def pt1(_in):
+    all_ingredients = []
+    for line in _in:
+        all_ingredients.extend(ingredients(line))
+
+    might_be = defaultdict(lambda: set(all_ingredients))
+    for line in _in:
+        for alg in allergens(line):
+            might_be[alg] &= set(ingredients(line))
+    might_be = set.union(*might_be.values())
+    defo_not = set(all_ingredients) - might_be
+    return sum(all_ingredients.count(ing) for ing in defo_not)
+
+
+def pt2(_in):
+    pass
+
+
+if __name__ == "__main__":
+    _in = aoc20.read_input(sys.argv[1:], 21)
+    print(pt1(_in))
+    print(pt2(_in))