2020: d07: ex2: add solution

2020/d07/ex2/ex2.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+
+import re
+import sys
+from dataclasses import dataclass
+from typing import Dict, List, Set, Tuple
+
+
+@dataclass(eq=True, frozen=True)  # Hashable
+class ColorInfo:
+    num: int
+    color: str
+
+
+Graph = Dict[str, Set[ColorInfo]]
+
+
+def extract_info(line: str) -> Tuple[str, Set[ColorInfo]]:
+    color_pattern = re.compile("(.*) contain ")
+    match = color_pattern.search(line)
+    assert match is not None
+    color = match.group(1).replace("bags", "bag")
+
+    line = line[match.end() : -1]  # Remove period at end of line
+
+    if line == "no other bags":
+        return color, set()
+
+    colors: Set[ColorInfo] = set()
+    pattern = re.compile("([0-9]+) (.*)")
+    for col in line.split(", "):
+        match = pattern.search(col)
+        assert match is not None
+        colors |= {
+            ColorInfo(int(match.group(1)), match.group(2).replace("bags", "bag"))
+        }
+
+    return color, colors
+
+
+def to_graph(raw: List[str]) -> Graph:
+    return {color: inside for color, inside in map(extract_info, raw)}
+
+
+def num_bags(graph: Graph, col: str) -> int:
+    return sum(
+        contained.num * (1 + num_bags(graph, contained.color))
+        for contained in graph[col]
+    )
+
+
+def solve(raw: List[str]) -> int:
+    graph = to_graph(raw)
+
+    return num_bags(graph, "shiny gold bag")
+
+
+def main() -> None:
+    input = [line.strip() for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()