Day 10: Hoof It

README.md

@@ -14,4 +14,4 @@ Development occurs in language-specific directories:
 |[Day7.hs](hs/src/Day7.hs)|[Day7.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day7.kt)|[day7.py](py/aoc2024/day7.py)|[day7.rs](rs/src/day7.rs)|
 |[Day8.hs](hs/src/Day8.hs)|[Day8.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day8.kt)|[day8.py](py/aoc2024/day8.py)|[day8.rs](rs/src/day8.rs)|
 |[Day9.hs](hs/src/Day9.hs)|[Day9.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day9.kt)|[day9.py](py/aoc2024/day9.py)|[day9.rs](rs/src/day9.rs)|
-|[Day10.hs](hs/src/Day10.hs)|[Day10.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day10.kt)|||
+|[Day10.hs](hs/src/Day10.hs)|[Day10.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day10.kt)|[day10.py](py/aoc2024/day10.py)||

py/aoc2024/day10.py

@@ -0,0 +1,68 @@
+"""
+Day 10: Hoof It
+"""
+
+from operator import add, or_
+from typing import Callable
+
+SAMPLE_INPUT = """
+89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732
+"""
+
+
+def _parse(data: str) -> list[set[tuple[int, int]]]:
+    elevations = [set() for _ in range(10)]
+    for y, line in enumerate(data.splitlines()):
+        for x, char in enumerate(line):
+            if "0" <= char <= "9":
+                elevations[int(char)].add((y, x))
+    return elevations
+
+
+def _adj(point: tuple[int, int]) -> list[tuple[int, int]]:
+    y, x = point
+    return [(y - 1, x), (y, x - 1), (y, x + 1), (y + 1, x)]
+
+
+def _bfs[T](
+    elevations: list[set[tuple[int, int]]],
+    start: Callable[[tuple[int, int]], T],
+    plus: Callable[[T, T], T],
+):
+    acc = {key: start(key) for key in elevations[0]}
+    for points in elevations[1:]:
+        tmp = {}
+        for key, value in acc.items():
+            for point in _adj(key):
+                if point in points:
+                    tmp[point] = plus(value, tmp[point]) if point in tmp else value
+        acc = tmp
+    return acc
+
+
+def part1(data: str) -> int:
+    """
+    >>> part1(SAMPLE_INPUT)
+    36
+    """
+    return sum(
+        len(value) for value in _bfs(_parse(data), lambda point: {point}, or_).values()
+    )
+
+
+def part2(data: str) -> int:
+    """
+    >>> part2(SAMPLE_INPUT)
+    81
+    """
+    return sum(_bfs(_parse(data), lambda _: 1, add).values())
+
+
+parts = (part1, part2)

py/pyproject.toml

@@ -33,6 +33,7 @@ day6 = "aoc2024.day6:parts"
 day7 = "aoc2024.day7:parts"
 day8 = "aoc2024.day8:parts"
 day9 = "aoc2024.day9:parts"
+day10 = "aoc2024.day10:parts"
 
 [build-system]
 requires = ["poetry-core"]