day 19, part 2 and part 1 optimized

19/2.py

@@ -0,0 +1,74 @@
+with open("input") as f:
+    content = [x.strip() for x in f]
+
+def parse_rule(rule):
+    name, rule = rule.split(": ")
+    rules = rule.split(" | ")
+    rules = [x.split(" ") for x in rules]
+    return name, rules
+
+def validate_message(rules, rule, message, pos):
+#    print(f"validating rule {rule} on {message}:{pos}")
+    if rules['11'] == rule:
+        count = 0
+        retval = True
+        while retval:
+            retval, new_p = validate_message(rules, rules['42'], message, pos)
+            if retval:
+                pos = new_p
+                count += 1
+        if count < 2:
+            return False, pos
+        count2 = 0
+        retval = True
+        while retval:
+            retval, new_p = validate_message(rules, rules['31'], message, pos)
+            if retval:
+                pos = new_p
+                count2 += 1
+        if count2 < 1 or count2 >= count:
+            return False, pos
+        return True, pos
+    elif rule[0][0].startswith("\""):
+        if pos >= len(message):
+            return False, pos
+        return rule[0][0][1] == message[pos], pos + 1
+    elif len(rule) == 2:
+        rv1, pos1 = validate_message(rules, [rule[0]], message, pos)
+        rv2, pos2 = validate_message(rules, [rule[1]], message, pos)
+        if rv1:
+            return rv1, pos1
+        elif rv2:
+            return rv2, pos2
+        else:
+            return False, pos
+    else:
+        p = pos
+        for x in rule[0]:
+            rv, new_p = validate_message(rules, rules[x], message, p)
+            if not rv:
+                return False, new_p
+            p = new_p
+        return True, p
+
+part = 0
+rules = {}
+messages = []
+for c in content:
+    if not c:
+        part += 1
+        continue
+    if part == 0: # parsing rules
+        name, rule = parse_rule(c)
+        rules[name] = rule
+    if part == 1: # reading messages
+        messages.append(c)
+
+retval = 0
+for m in messages:
+    rv, pos = validate_message(rules, rules['11'], m, 0)
+    if rv and pos == len(m):
+        print(m)
+        retval += 1
+
+print(retval)