2024 day 15 part 2

Author: lancelote

README.md

@@ -15,7 +15,7 @@
 - 2021 - ★★★★★ ★★★★★ ★★★★★ ★★★
 - 2022 - ★★★★★ ★★★★★ ★★★★★ ★☆
 - 2023 - ★★★★★ ★★★★★ ★★★★★ ★★★☆
-- 2024 - ★★★★★ ★★★★★ ★★★★☆
+- 2024 - ★★★★★ ★★★★★ ★★★★★
 
 ## How to use
 

src/year2024/day15b.py

@@ -0,0 +1,193 @@
+"""2024 - Day 15 Part 2: Warehouse Woes"""
+
+from __future__ import annotations
+
+from abc import ABC
+from abc import abstractmethod
+from dataclasses import dataclass
+from enum import StrEnum
+
+
+class Instruction(StrEnum):
+    NORTH = "^"
+    EAST = ">"
+    SOUTH = "v"
+    WEST = "<"
+
+
+SHIFTS = {
+    # dr, dc
+    Instruction.NORTH: (-1, 0),
+    Instruction.EAST: (0, +1),
+    Instruction.SOUTH: (+1, 0),
+    Instruction.WEST: (0, -1),
+}
+
+
+@dataclass
+class Object(ABC):
+    symbol: str
+    r: int
+    c: int
+
+    @abstractmethod
+    def can_move(self, instruction: Instruction, warehouse: Warehouse) -> bool:
+        raise NotImplementedError
+
+    @abstractmethod
+    def move(self, instruction: Instruction, warehouse: Warehouse) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def update_position(self, nr: int, nc: int, warehouse: Warehouse) -> None:
+        raise NotImplementedError
+
+
+class Bulky(Object, ABC):
+    def can_move(self, instruction: Instruction, warehouse: Warehouse) -> bool:
+        moveable = True
+
+        dr, dc = SHIFTS[instruction]
+        nr, nc = self.r + dr, self.c + dc
+
+        if (nr, nc) in warehouse.objects:
+            neighbor1 = warehouse.objects[(nr, nc)]
+            moveable &= neighbor1 is self or neighbor1.can_move(
+                instruction, warehouse
+            )
+        if (nr, nc + 1) in warehouse.objects:
+            neighbor2 = warehouse.objects[(nr, nc + 1)]
+            moveable &= neighbor2 is self or neighbor2.can_move(
+                instruction, warehouse
+            )
+
+        return moveable
+
+    def move(self, instruction: Instruction, warehouse: Warehouse) -> None:
+        if self.can_move(instruction, warehouse):
+            dr, dc = SHIFTS[instruction]
+            nr, nc = self.r + dr, self.c + dc
+
+            if (nr, nc) in warehouse.objects:
+                neighbor = warehouse.objects[(nr, nc)]
+                if neighbor is not self:
+                    neighbor.move(instruction, warehouse)
+
+            if (nr, nc + 1) in warehouse.objects:
+                neighbor = warehouse.objects[(nr, nc + 1)]
+                if neighbor is not self:
+                    neighbor.move(instruction, warehouse)
+
+            self.update_position(nr, nc, warehouse)
+
+    def update_position(self, nr: int, nc: int, warehouse: Warehouse) -> None:
+        del warehouse.objects[(self.r, self.c)]
+        del warehouse.objects[(self.r, self.c + 1)]
+
+        self.r, self.c = nr, nc
+
+        warehouse.objects[(nr, nc)] = self
+        warehouse.objects[(nr, nc + 1)] = self
+
+
+class Wall(Bulky):
+    def can_move(self, instruction: Instruction, warehouse: Warehouse) -> bool:
+        return False
+
+    def move(self, instruction: Instruction, warehouse: Warehouse) -> None: ...
+
+
+class Box(Bulky):
+    @property
+    def gps(self) -> int:
+        return self.r * 100 + self.c
+
+
+class Robot(Object):
+    def can_move(self, instruction: Instruction, warehouse: Warehouse) -> bool:
+        dr, dc = SHIFTS[instruction]
+        nr, nc = self.r + dr, self.c + dc
+
+        if (nr, nc) in warehouse.objects:
+            neighbor = warehouse.objects[(nr, nc)]
+            return neighbor.can_move(instruction, warehouse)
+        else:
+            return True
+
+    def move(self, instruction: Instruction, warehouse: Warehouse) -> None:
+        if self.can_move(instruction, warehouse):
+            dr, dc = SHIFTS[instruction]
+            nr, nc = self.r + dr, self.c + dc
+            if (nr, nc) in warehouse.objects:
+                neighbor = warehouse.objects[(nr, nc)]
+                neighbor.move(instruction, warehouse)
+            self.update_position(nr, nc, warehouse)
+
+    def update_position(self, nr: int, nc: int, warehouse: Warehouse) -> None:
+        del warehouse.objects[(self.r, self.c)]
+        self.r, self.c = nr, nc
+        warehouse.objects[(nr, nc)] = self
+
+
+@dataclass
+class Warehouse:
+    height: int
+    width: int
+    robot: Robot
+    objects: dict[tuple[int, int], Object]
+    boxes: list[Box]
+
+    @classmethod
+    def from_text(cls, text: str) -> Warehouse:
+        robot = Robot(r=0, c=0, symbol="@")
+        objects: dict[tuple[int, int], Object] = {}
+        boxes: list[Box] = []
+
+        lines = text.split("\n")
+        height, width = len(lines), len(lines[0] * 2)
+
+        for r, row in enumerate(lines):
+            for c, x in enumerate(row):
+                if x == "#":
+                    wall = Wall("#", r, c * 2)
+                    objects[(r, c * 2)] = wall
+                    objects[(r, c * 2 + 1)] = wall
+                elif x == "@":
+                    robot.r, robot.c = r, c * 2
+                    objects[(r, c * 2)] = robot
+                elif x == "O":
+                    box = Box("O", r, c * 2)
+                    boxes.append(box)
+                    objects[(r, c * 2)] = box
+                    objects[(r, c * 2 + 1)] = box
+
+        return cls(height, width, robot, objects, boxes)
+
+    def move_robot(self, instructions: list[Instruction]) -> None:
+        for instruction in instructions:
+            self.robot.move(instruction, self)
+
+    @property
+    def gps_sum(self) -> int:
+        return sum(box.gps for box in self.boxes)
+
+    def __str__(self) -> str:
+        lines = [["."] * self.width for _ in range(self.height)]
+
+        for (r, c), v in self.objects.items():
+            lines[r][c] = v.symbol
+
+        return "\n".join("".join(line) for line in lines)
+
+
+def process_data(task: str) -> tuple[Warehouse, list[Instruction]]:
+    first, second = task.split("\n\n")
+    warehouse = Warehouse.from_text(first)
+    instructions = [Instruction(x) for x in second if x in Instruction]
+    return warehouse, instructions
+
+
+def solve(task: str) -> int:
+    warehouse, instructions = process_data(task)
+    warehouse.move_robot(instructions)
+    return warehouse.gps_sum

tests/src/year2024/test_day15b.py

@@ -0,0 +1,34 @@
+"""2024 - Day 15 Part 2: Warehouse Woes"""
+
+from textwrap import dedent
+
+from src.year2024.day15b import solve
+
+
+def test_solve_large():
+    task = dedent(
+        """
+        ##########
+        #..O..O.O#
+        #......O.#
+        #.OO..O.O#
+        #..O@..O.#
+        #O#..O...#
+        #O..O..O.#
+        #.OO.O.OO#
+        #....O...#
+        ##########
+
+        <vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
+        vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
+        ><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
+        <<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
+        ^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
+        ^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
+        >^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
+        <><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
+        ^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
+        v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^
+        """
+    ).strip()
+    assert solve(task) == 9021