From 3e709cc86394b86b2207bf256c5b09a8a2cc4eef Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Tue, 10 Dec 2024 09:38:31 +0100
Subject: [PATCH] Implement 2024 day 10

---
 2024/src/aoc/days/day10.py | 85 ++++++++++++++++++++++++++++++++++++++
 2024/tests/samples/10.txt  |  8 ++++
 2024/tests/test_day10.py   |  7 ++++
 3 files changed, 100 insertions(+)
 create mode 100644 2024/src/aoc/days/day10.py
 create mode 100644 2024/tests/samples/10.txt
 create mode 100644 2024/tests/test_day10.py

diff --git a/2024/src/aoc/days/day10.py b/2024/src/aoc/days/day10.py
new file mode 100644
index 0000000..9a76c4d
--- /dev/null
+++ b/2024/src/aoc/days/day10.py
@@ -0,0 +1,85 @@
+from collections import deque
+
+import numpy
+
+from . import SeparateRunner
+
+
+class DayRunner(SeparateRunner):
+    @classmethod
+    def part1(cls, input: str) -> int:
+        grid = numpy.array(
+            [[int(v) for v in line] for line in input.strip().split("\n")]
+        )
+
+        width, height = grid.shape
+
+        start_x, start_y = numpy.nonzero(grid == 0)
+
+        todo = []
+
+        reachable = 0
+
+        for sx, sy in zip(start_x, start_y):
+            todo.append((sx, sy))
+            ways = numpy.zeros_like(grid, dtype=bool)
+
+            def enqueue(x: int, y: int, val: int) -> None:
+                if grid[x, y] == val + 1:
+                    if not ways[x, y]:
+                        todo.append((x, y))
+                    ways[x, y] += True
+
+            while todo:
+                x, y = todo.pop()
+                val = grid[x, y]
+                if val == 9:
+                    reachable += 1
+                    continue
+
+                if x > 0:
+                    enqueue(x - 1, y, val)
+                if y > 0:
+                    enqueue(x, y - 1, val)
+                if x < width - 1:
+                    enqueue(x + 1, y, val)
+                if y < height - 1:
+                    enqueue(x, y + 1, val)
+
+        return reachable
+
+    @classmethod
+    def part2(cls, input: str) -> int:
+        grid = numpy.array(
+            [[int(v) for v in line] for line in input.strip().split("\n")]
+        )
+        ways = numpy.zeros_like(grid)
+
+        width, height = grid.shape
+
+        start_x, start_y = numpy.nonzero(grid == 9)
+        ways[grid == 9] = 1
+
+        todo = deque((x, y) for x, y in zip(start_x, start_y))
+
+        def enqueue(x: int, y: int, val: int, cur: int) -> None:
+            if grid[x, y] == val - 1:
+                if ways[x, y] == 0:
+                    todo.append((x, y))
+                ways[x, y] += cur
+
+        while todo:
+            x, y = todo.popleft()
+            val = grid[x, y]
+            cur = ways[x, y]
+
+            if x > 0:
+                enqueue(x - 1, y, val, cur)
+            if y > 0:
+                enqueue(x, y - 1, val, cur)
+            if x < width - 1:
+                enqueue(x + 1, y, val, cur)
+            if y < height - 1:
+                enqueue(x, y + 1, val, cur)
+
+        return ways[grid == 0].sum()
diff --git a/2024/tests/samples/10.txt b/2024/tests/samples/10.txt
new file mode 100644
index 0000000..cada9b3
--- /dev/null
+++ b/2024/tests/samples/10.txt
@@ -0,0 +1,8 @@
+89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732
diff --git a/2024/tests/test_day10.py b/2024/tests/test_day10.py
new file mode 100644
index 0000000..68fd47f
--- /dev/null
+++ b/2024/tests/test_day10.py
@@ -0,0 +1,7 @@
+from aoc.days.day10 import DayRunner
+
+from . import get_data
+
+
+def test_sample_part1() -> None:
+    assert DayRunner.part1(get_data(10)) == 36