2023: d02: ex2: add solution

2023/d02/ex2/ex2.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python
+
+import math
+import sys
+from collections import Counter
+from enum import StrEnum
+
+
+class Color(StrEnum):
+    RED = "red"
+    GREEN = "green"
+    BLUE = "blue"
+
+
+Round = Counter[Color]
+Game = list[Round]
+
+# The input is in order without skipping, but just in case...
+GameRecord = dict[int, Game]
+
+BAG_CONTENTS = Counter(
+    {
+        Color.RED: 12,
+        Color.GREEN: 13,
+        Color.BLUE: 14,
+    }
+)
+
+
+def solve(input: list[str]) -> int:
+    def parse_round(round: str) -> Round:
+        values = (value.split(" ") for value in round.split(", "))
+        return Counter({Color(c): int(n) for n, c in values})
+
+    # This does *not* expect the "Game <int>:" bit
+    def parse_game(game: str) -> Game:
+        rounds = game.split("; ")
+        return [parse_round(r) for r in rounds]
+
+    def parse_line(line: str) -> tuple[int, Game]:
+        game_id, rounds = line.split(": ")
+        return int(game_id.removeprefix("Game ")), parse_game(rounds)
+
+    def parse(input: list[str]) -> GameRecord:
+        parsed = map(parse_line, input)
+        return {id: game for id, game in parsed}
+
+    def min_cubes(game: Game) -> dict[Color, int]:
+        res = Counter({c: 0 for c in Color})
+
+        for r in game:
+            res |= r
+
+        return res
+
+    def power(game: Game) -> int:
+        return math.prod(min_cubes(game).values())
+
+    games = parse(input)
+    return sum(map(power, games.values()))
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()