2024 day 10.

src/holt59/aoc/2024/day10.py

@@ -3,5 +3,44 @@ from typing import Any, Iterator
 from ..base import BaseSolver
 
 
+def process(
+    grid: list[list[int]], current: tuple[int, int]
+) -> set[tuple[tuple[int, int], ...]]:
+    row, col = current
+
+    if grid[row][col] == 9:
+        return {((row, col),)}
+
+    result: set[tuple[tuple[int, int], ...]] = set()
+
+    for di, dj in ((-1, 0), (0, 1), (1, 0), (0, -1)):
+        i, j = row + di, col + dj
+
+        if i < 0 or i >= len(grid) or j < 0 or j >= len(grid[row]):
+            continue
+
+        if grid[i][j] != grid[row][col] + 1:
+            continue
+
+        for path in process(grid, (i, j)):
+            result.add(((row, col),) + path)
+
+    return result
+
+
 class Solver(BaseSolver):
-    def solve(self, input: str) -> Iterator[Any]: ...
+    def solve(self, input: str) -> Iterator[Any]:
+        grid = [[int(col) for col in row] for row in input.splitlines()]
+        n_rows, n_cols = len(grid), len(grid[0])
+
+        heads = [
+            (i, j) for i in range(n_rows) for j in range(n_cols) if grid[i][j] == 0
+        ]
+
+        # for head in heads:
+        #     print(head, process(grid, head))
+
+        paths = {head: process(grid, head) for head in heads}
+
+        yield sum(len({path[-1] for path in paths[head]}) for head in heads)
+        yield sum(len(paths[head]) for head in heads)