Day 18: Python (part 1)

Test doesn't work on the example: n=7 (the actual grid size) outputs a
path length of 18 instead of 22. Must set n=9 to obtain the correct
result.

18/python/solution.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+"""AoC day 18, 2024: RAM Run"""
+
+import pathlib
+import sys
+from collections import deque
+
+from utils import ilist
+
+
+def parse_data(puzzle_input: str) -> list[list[int]]:
+    """Parse input data"""
+    return [ilist(line, sep=",") for line in puzzle_input.splitlines()]
+
+
+def part1(data: list[list[int]], n: int = 70, bytes: int = 1024) -> int:
+    """Solve part 1"""
+    grid = [[0] * (n + 1) for _ in range(n + 1)]
+    for col, row in data[:bytes]:
+        grid[row][col] = 1
+
+    queue = deque([(0, 0, 0)])
+    seen = {(0, 0)}
+
+    while queue:
+        row, col, distance = queue.popleft()
+        for nr, nc in ((row + 1, col), (row, col + 1), (row - 1, col), (row, col - 1)):
+            if nr < 0 or nc < 0 or nr > n or nc > n:
+                continue
+            if (nr, nc) in seen:
+                continue
+            if grid[nr][nc] == 1:
+                continue
+            if nr == nc == n:
+                return distance + 1
+            seen.add((nr, nc))
+            queue.append((nr, nc, distance + 1))
+    return 0
+
+
+def part2(data: list[list[int]]) -> int:
+    """Solve part 2"""
+    return 0
+
+
+def solve(puzzle_input: str) -> tuple[int, int]:
+    """Solve the puzzle for the given input"""
+    data = parse_data(puzzle_input)
+    return part1(data), part2(data)
+
+
+if __name__ == "__main__":
+    for path in sys.argv[1:]:
+        print(f"\n{path}:")
+        solutions = solve(pathlib.Path(path).read_text().strip())
+        print("\n".join(str(solution) for solution in solutions))

18/python/test_solution.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+"""Tests for AoC day 18, 2024: RAM Run"""
+
+from pathlib import Path
+
+import pytest
+
+from solution import parse_data, part1, part2
+
+
+@pytest.fixture
+def example_data() -> str:
+    current_dir = Path(__file__).parent
+    filename = current_dir.parent / "example.txt"
+    try:
+        return filename.read_text().strip()
+    except FileNotFoundError:
+        raise FileNotFoundError(f"Example input file not found at {filename}")
+
+
+def test_parse(example_data: str) -> None:
+    data = parse_data(example_data)
+    assert len(data) > 0
+
+
+def test_part1(example_data: str) -> None:
+    data = parse_data(example_data)
+    # FIXME: `n` is wrong for the example, it doesn't match the grid size
+    assert part1(data, n=9, bytes=12) == 22
+
+
+def test_part2(example_data: str) -> None:
+    data = parse_data(example_data)
+    assert part2(data) == 0  # FIXME: replace with expected result for Part 2