From 7ec2081eea936bb621a46da7fcda22e5fc0fee2d Mon Sep 17 00:00:00 2001
From: Daniel Lin <ephemient@gmail.com>
Date: Sat, 24 Dec 2022 05:24:06 -0500
Subject: [PATCH] Day 24: Blizzard Basin

---
 README.md           |  2 +-
 py/aoc2022/day24.py | 62 +++++++++++++++++++++++++++++++++++++++++++++
 py/pyproject.toml   |  1 +
 3 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 py/aoc2022/day24.py

diff --git a/README.md b/README.md
index 372d47d..6f9ab8d 100644
--- a/README.md
+++ b/README.md
@@ -29,4 +29,4 @@ Development occurs in language-specific directories:
 |[Day21.hs](hs/src/Day21.hs)|[Day21.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day21.kt)|[day21.py](py/aoc2022/day21.py)|[day21.rs](rs/src/day21.rs)|
 |[Day22.hs](hs/src/Day22.hs)|[Day22.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day22.kt)|[day22.py](py/aoc2022/day22.py)|[day22.rs](rs/src/day22.rs)|
 |[Day23.hs](hs/src/Day23.hs)|[Day23.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day23.kt)|[day23.py](py/aoc2022/day23.py)|[day23.rs](rs/src/day23.rs)|
-|[Day24.hs](hs/src/Day24.hs)|[Day24.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day24.kt)|
+|[Day24.hs](hs/src/Day24.hs)|[Day24.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day24.kt)|[day24.py](py/aoc2022/day24.py)|
diff --git a/py/aoc2022/day24.py b/py/aoc2022/day24.py
new file mode 100644
index 0000000..d33c7bb
--- /dev/null
+++ b/py/aoc2022/day24.py
@@ -0,0 +1,62 @@
+"""
+Day 24: Blizzard Basin
+"""
+
+import heapq
+
+SAMPLE_INPUT = ["#.######", "#>>.<^<#", "#.<..<<#", "#>v.><>#", "#<^v^^>#", "######.#"]
+
+
+def _search(lines, start, end, time=0):
+    end_x, end_y = end
+    seen, queue = {(start, time)}, [(0, (start, time))]
+    while queue:
+        position, time = heapq.heappop(queue)[1]
+        if position == end:
+            return time
+        x, y = position
+        time += 1
+        for x, y in [(x - 1, y), (x, y - 1), (x, y), (x, y + 1), (x + 1, y)]:
+            if y < 0 or y >= len(lines) or x < 1 or x >= len(line := lines[y]) - 1:
+                continue
+            if y in (0, len(lines) - 1):
+                if line[x] != ".":
+                    continue
+            elif lines[y][(x - 1 + time) % (len(line) - 2) + 1] == "<":
+                continue
+            elif lines[y][(x - 1 - time) % (len(line) - 2) + 1] == ">":
+                continue
+            elif lines[(y - 1 + time) % (len(lines) - 2) + 1][x] == "^":
+                continue
+            elif lines[(y - 1 - time) % (len(lines) - 2) + 1][x] == "v":
+                continue
+            state = ((x, y), time)
+            if state not in seen:
+                seen.add(state)
+                heapq.heappush(queue, (time + abs(x - end_x) + abs(y - end_y), state))
+    raise LookupError()
+
+
+def part1(lines):
+    """
+    >>> part1(SAMPLE_INPUT)
+    18
+    """
+    lines = [line.rstrip() for line in lines]
+    return _search(lines, (1, 0), (len(lines[-1]) - 2, len(lines) - 1))
+
+
+def part2(lines):
+    """
+    >>> part2(SAMPLE_INPUT)
+    54
+    """
+    lines = [line.rstrip() for line in lines]
+    start = (1, 0)
+    end = (len(lines[-1]) - 2, len(lines) - 1)
+    return _search(
+        lines, start, end, _search(lines, end, start, _search(lines, start, end))
+    )
+
+
+parts = (part1, part2)
diff --git a/py/pyproject.toml b/py/pyproject.toml
index ac04040..01b3625 100644
--- a/py/pyproject.toml
+++ b/py/pyproject.toml
@@ -55,6 +55,7 @@ day20 = "aoc2022.day20:parts"
 day21 = "aoc2022.day21:parts"
 day22 = "aoc2022.day22:parts"
 day23 = "aoc2022.day23:parts"
+day24 = "aoc2022.day24:parts"
 
 [tool.black]
 target_version = ["py311"]