2015: d21: ex1: add solution

2015/d21/ex1/ex1.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+from collections.abc import Iterator
+from typing import NamedTuple
+
+
+class Ennemy(NamedTuple):
+    hp: int
+    damage: int
+    armor: int
+
+    def attack(self, other: "Ennemy") -> "Ennemy":
+        return Ennemy(
+            other.hp - max(1, self.damage - other.armor),
+            other.damage,
+            other.armor,
+        )
+
+
+class Item(NamedTuple):
+    cost: int
+    damage: int
+    armor: int
+
+
+WEAPONS = {
+    "Dagger": Item(8, 4, 0),
+    "Shortsword": Item(10, 5, 0),
+    "Warhammer": Item(25, 6, 0),
+    "Longsword": Item(40, 7, 0),
+    "Greataxe": Item(74, 8, 0),
+}
+ARMORS = {
+    "Leather": Item(13, 0, 1),
+    "Chainmail": Item(31, 0, 2),
+    "Splintmail": Item(53, 0, 3),
+    "Bandedmail": Item(75, 0, 4),
+    "Platemail": Item(102, 0, 5),
+}
+RINGS = {
+    "Damage +1": Item(25, 1, 0),
+    "Damage +2": Item(50, 2, 0),
+    "Damage +3": Item(100, 3, 0),
+    "Defense +1": Item(20, 0, 1),
+    "Defense +2": Item(40, 0, 2),
+    "Defense +3": Item(80, 0, 3),
+}
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> Ennemy:
+        return Ennemy(*map(int, (line.split(": ")[1] for line in input.splitlines())))
+
+    def choose_items() -> Iterator[list[Item]]:
+        allowed_weapons = [1]
+        allowed_armors = [0, 1]
+        allowed_rings = [0, 1, 2]
+
+        for weapons, armors, rings in itertools.product(
+            itertools.chain.from_iterable(
+                itertools.combinations(WEAPONS.values(), i) for i in allowed_weapons
+            ),
+            itertools.chain.from_iterable(
+                itertools.combinations(ARMORS.values(), i) for i in allowed_armors
+            ),
+            itertools.chain.from_iterable(
+                itertools.combinations(RINGS.values(), i) for i in allowed_rings
+            ),
+        ):
+            yield list(itertools.chain(weapons, armors, rings))
+
+    def assemble_inventory(items: list[Item]) -> Ennemy:
+        return Ennemy(
+            hp=100,
+            damage=sum(item.damage for item in items),
+            armor=sum(item.armor for item in items),
+        )
+
+    def battle(us: Ennemy, ennemy: Ennemy) -> bool:
+        while True:
+            ennemy = us.attack(ennemy)
+            if ennemy.hp <= 0:
+                return True
+            us = ennemy.attack(us)
+            if us.hp <= 0:
+                return False
+
+    ennemy = parse(input)
+    return min(
+        sum(item.cost for item in items)
+        for items in choose_items()
+        if battle(assemble_inventory(items), ennemy)
+    )
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()