1 files changed, 84 insertions, 0 deletions
diff --git a/2020/19/puzzle-2.py b/2020/19/puzzle-2.py
new file mode 100755
index 0000000..b0efe15
--- /dev/null
+++ b/2020/19/puzzle-2.py
@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+
+from collections import OrderedDict
+from re import search
+
+
+def check(test: str, patterns: dict[str, list[str]]) -> bool:
+	chunks = string_divide(test, 8)
+	search_str = ""
+
+	for chunk in chunks:
+		if chunk in patterns["42"]:
+			search_str += "0"
+		elif chunk in patterns["31"]:
+			search_str += "1"
+		else:
+			return False
+
+	# 42 = 0, 31 = 1
+	res = search(r"^(0)+(1)+$", search_str)
+	return not (not res or search_str.count("0") <= search_str.count("1"))
+
+
+def string_divide(string: str, div: int) -> list[str]:
+	l: list[str] = []
+	for i in range(0, len(string), div):
+		l.append(string[i : i + div])
+	return l
+
+
+def main() -> None:
+	with open("input", "r") as f:
+		data = f.readlines()
+
+	i = 0
+	rules: list[tuple[str]] = []
+	while data[i] != "\n":
+		rules.append(tuple(x for x in tuple(data[i].split(": "))))
+		i += 1
+
+	tests: list[str] = []
+	for line in data:
+		tests.append(line.strip())
+
+	patterns: dict[str, list[str]] = {}
+
+	# Get "a" and "b" out of the way to do less comparisons in the next loop. Also make use of
+	# this loop to strip newlines off of all the rules.
+	for rule in rules:
+		rules[rules.index(rule)] = (rule[0], rule[1].strip())
+		if len(rule[1]) == 4:
+			patterns[rule[0]] = [rule[1][1]]
+
+	while len(patterns) != len(rules):
+		for rule in rules:
+			if rule[0] in patterns:
+				continue
+
+			res = rule[1].split(" | ")
+			req_rules = list(OrderedDict.fromkeys(" ".join(res).split(" ")))
+			all_in = True
+			for req in req_rules:
+				if req not in patterns:
+					all_in = False
+					break
+			if all_in == True:
+				all_combos: list[str] = []
+				for re in res:
+					re = re.split(" ")
+					if len(re) == 1:
+						all_combos.extend(patterns[re[0]])
+					else:
+						for x in patterns[re[0]]:
+							for y in patterns[re[1]]:
+								all_combos.append(f"{x}{y}")
+						all_combos = list(OrderedDict.fromkeys(all_combos))
+
+				patterns[rule[0]] = all_combos
+
+	print(len([test for test in tests if check(test, patterns)]))
+
+
+if __name__ == "__main__":
+	main()