2024 day 16

Author: Peter554

2024/python/data/day16/example_1.txt

@@ -0,0 +1,15 @@
+###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############

2024/python/data/day16/example_2.txt

@@ -0,0 +1,17 @@
+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################

2024/python/data/day16/input.txt

@@ -5,6 +5,7 @@ description = "Advent of Code 2024"
 readme = "README.md"
 requires-python = ">=3.13"
 dependencies = [
+    "frozendict>=2.4.7",
     "z3-solver>=4.15.4.0",
 ]
 

2024/python/pyproject.toml

@@ -0,0 +1,93 @@
+from __future__ import annotations
+
+import heapq
+import itertools
+from dataclasses import dataclass
+from pathlib import Path
+
+from frozendict import frozendict
+
+
+def part_1(input: Path) -> int:
+    start, end, walls = parse_input(input)
+    lowest_scores = find_lowest_scores(start, end, walls)
+    return min([score for state, score in lowest_scores.items() if state.p == end])
+
+
+def parse_input(input: Path) -> tuple[P, P, frozenset[P]]:
+    start: P | None = None
+    end: P | None = None
+    walls: set[P] = set()
+    for y, line in enumerate(input.read_text().splitlines()):
+        for x, c in enumerate(line):
+            if c == "#":
+                walls.add(P(x, y))
+            elif c == "S":
+                start = P(x, y)
+            elif c == "E":
+                end = P(x, y)
+    assert start is not None
+    assert end is not None
+    return start, end, frozenset(walls)
+
+
+def find_lowest_scores(start: P, end: P, walls: frozenset[P]) -> frozendict[State, int]:
+    counter = itertools.count()
+    q = [(0, next(counter), State(start, P(1, 0)))]
+    scores = {}
+    while q:
+        score, _, state = heapq.heappop(q)
+        if state in scores:
+            continue
+
+        scores[state] = score
+
+        heapq.heappush(
+            q,
+            (score + 1000, next(counter), State(state.p, CLOCKWISE[state.d])),  # ty: ignore[invalid-argument-type]
+        )
+        heapq.heappush(
+            q,
+            (score + 1000, next(counter), State(state.p, ANTICLOCKWISE[state.d])),  # ty: ignore[invalid-argument-type]
+        )
+        if state.p + state.d not in walls:
+            heapq.heappush(
+                q,
+                (score + 1, next(counter), State(state.p + state.d, state.d)),
+            )
+
+    return frozendict(scores)
+
+
+@dataclass(frozen=True)
+class State:
+    p: P
+    d: P
+
+
+@dataclass(frozen=True)
+class P:
+    x: int
+    y: int
+
+    def __add__(self, other: P) -> P:
+        return P(self.x + other.x, self.y + other.y)
+
+
+CLOCKWISE = frozendict(
+    {
+        P(1, 0): P(0, 1),
+        P(0, 1): P(-1, 0),
+        P(-1, 0): P(0, -1),
+        P(0, -1): P(1, 0),
+    }
+)
+
+ANTICLOCKWISE = frozendict(
+    {
+        P(1, 0): P(0, -1),
+        P(0, 1): P(1, 0),
+        P(-1, 0): P(0, 1),
+        P(0, -1): P(-1, 0),
+    }
+)

2024/python/src/aoc2024/day16.py

@@ -0,0 +1,17 @@
+from pathlib import Path
+
+from aoc2024 import day16
+
+DATA_DIR = Path(__file__).parent.parent / "data/day16"
+
+
+def test_part_1():
+    assert day16.part_1(DATA_DIR / "example_1.txt") == 7036
+    assert day16.part_1(DATA_DIR / "example_2.txt") == 11048
+    assert day16.part_1(DATA_DIR / "input.txt") == 127520
+
+
+# def test_part_2():
+#     assert day16.part_2(DATA_DIR / "example_1.txt") == 45
+#     assert day16.part_2(DATA_DIR / "example_2.txt") == 64
+#     assert day16.part_2(DATA_DIR / "input.txt") == 42