1 files changed, 58 insertions, 0 deletions
diff --git a/2020/aoc2020-d19.py b/2020/aoc2020-d19.py
new file mode 100644
index 0000000..fb4497d
--- /dev/null
+++ b/2020/aoc2020-d19.py
@@ -0,0 +1,58 @@
+#advent of code 2020
+#day 19
+import re
+
+def FindRule(r,d):
+	if d >20: return "";
+	elif type(rules[r]) == str:
+		return rules[r];
+	else:
+		suboptions = [];
+		for subset in rules[r]:
+			subopt = "(";
+			for sr in subset:
+				subopt += FindRule(sr,d+1);
+			subopt += ")";
+			suboptions.append(subopt);
+		return "(" + "|".join(suboptions) + ")";
+
+rules = dict();
+PuzzleInput = open("19.in","r").read().split("\n\n");
+rules_raw = PuzzleInput[0].split("\n");
+messages = PuzzleInput[1].split("\n");
+for rule in rules_raw:
+	rule_i, rule_vals = rule.split(": ");
+	rule_i = int(rule_i);
+	if rule_vals[0] == '"':
+		rules[rule_i] = rule_vals[1];
+	else:
+		rules[rule_i] = [[int(r) for r in subrule.split(" ")] for subrule in rule_vals.split(" | ")];
+
+TotalRule = "";
+TotalRule = FindRule(0,0);
+regsearch = re.compile(TotalRule);
+
+p1 = 0;
+for message in messages:
+	message = message.replace("\n","");
+	regfind = regsearch.fullmatch(message);
+	if regfind != None:
+		p1+=1;
+	
+print("part 1 =",p1);
+#part 2: change of rules 8 and 11
+rules[8] = [[42], [42, 8]];
+rules[11] = [[42,31], [42,11,31]];
+TotalRule = "";
+TotalRule = FindRule(0,0);
+p2 = 0;
+for countdown,message in enumerate(messages):
+	#print(len(messages) - countdown, len(messages));
+	message = message.replace("\n","");
+	regfind = re.findall(TotalRule+"+",message);
+	if regfind:
+		for x in regfind: 
+			if message in x:
+				p2+=1;
+				break;
+print("part 2 =",p2);