Create day19.py

2020/Python/day19.py

@@ -0,0 +1,56 @@
+import re
+from typing import Union
+from functools import partial
+
+
+def parse_data():
+    rules = {}
+    strings = []
+    with open("input.txt") as file:
+        for line in file:
+            line = line.rstrip()
+
+            if not line:
+                continue
+
+            if line[0].isdigit():
+                rule_id, rule_or = line.split(": ")
+                rule_id = int(rule_id)
+                rule_or = rule_or.split(" | ")
+                rule_entry = []
+                if rule_or[0][0] == '"':
+                    rules[rule_id] = rule_or[0][1]
+                else:
+                    for rule in rule_or:
+                        rule_entry.append(list(map(int, rule.split(" "))))
+                    rules[rule_id] = rule_entry
+            else:
+                strings.append(line)
+
+    return rules, strings
+
+
+def solve_p1(rules, strings) -> int:
+
+    def convert_to_regex(rules, rule_idx: int) -> str:
+        rule = rules[rule_idx]
+        if isinstance(rule, str):
+            return rule
+        else:
+            out = "("
+            map_func = partial(convert_to_regex, rules)
+            for rule_option in rule:
+                out += "".join(map(map_func, rule_option)) + "|"
+            return out[:-1] + ")"
+
+    pattern_str = convert_to_regex(rules, 0)+"$"
+    pattern = re.compile(pattern_str)
+    matching = 0
+    for string in strings:
+        if pattern.match(string):
+            matching += 1
+    return matching
+
+
+RULES, STRINGS = parse_data()
+print(solve_p1(RULES, STRINGS))