chore: create new project structure and aoc.py runner script

adventofcode/2020/day7/day7.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+import re
+from collections import defaultdict, deque
+
+
+def main(input_rules):
+    rules = parse_rules(input_rules)
+    reverse_rules = build_reverse_rules(rules)
+    print(part1(reverse_rules))
+    print(part2(rules, "shiny gold"))
+
+
+def parse_rules(input_rules):
+    rules = {}
+    for input_rule in input_rules:
+        color, rule = input_rule.split(" bags contain ")
+        rules[color] = {color: int(number) for number, color in re.findall(r'(\d+) (\w+ \w+)', rule)}
+    return rules
+
+
+def build_reverse_rules(rules):
+    reverse_rules = defaultdict(list)
+    for bag, inner_rules in rules.items():
+        for c in inner_rules:
+            reverse_rules[c].append(bag)
+    return reverse_rules
+
+
+def part1(reverse_rules):
+    queue  = deque(("shiny gold",))
+    may_contain_shiny_gold = set()
+    while queue:
+        color = queue.pop()
+        for c in reverse_rules.get(color, []):
+            if c not in may_contain_shiny_gold:
+                may_contain_shiny_gold.add(c)
+                queue.appendleft(c)
+    return len(may_contain_shiny_gold)
+
+
+def part2(rules, color):
+    return sum(number + number * part2(rules, c) for c, number in rules[color].items())
+
+
+if __name__ == "__main__":
+    import fileinput
+    main(fileinput.input())