From 1e644e14f1d34e35c16378f39654b14940844f9f Mon Sep 17 00:00:00 2001
From: Daniel Lin <ephemient@gmail.com>
Date: Thu, 14 Dec 2023 04:55:26 -0500
Subject: [PATCH] Day 14: Parabolic Reflector Dish

---
 README.md           |  2 +-
 py/aoc2023/day14.py | 76 +++++++++++++++++++++++++++++++++++++++++++++
 py/pyproject.toml   |  1 +
 3 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 py/aoc2023/day14.py

diff --git a/README.md b/README.md
index 390c0739..8621f03f 100644
--- a/README.md
+++ b/README.md
@@ -18,4 +18,4 @@ Development occurs in language-specific directories:
 |[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day11.kt)|[day11.py](py/aoc2023/day11.py)|[day11.rs](rs/src/day11.rs)|
 |[Day12.hs](hs/src/Day12.hs)|[Day12.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day12.kt)|[day12.py](py/aoc2023/day12.py)|[day12.rs](rs/src/day12.rs)|
 |[Day13.hs](hs/src/Day13.hs)|[Day13.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day13.kt)|[day13.py](py/aoc2023/day13.py)|[day13.rs](rs/src/day13.rs)|
-|[Day14.hs](hs/src/Day14.hs)|[Day14.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day14.kt)|||
+|[Day14.hs](hs/src/Day14.hs)|[Day14.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day14.kt)|[day14.py](py/aoc2023/day14.py)||
diff --git a/py/aoc2023/day14.py b/py/aoc2023/day14.py
new file mode 100644
index 00000000..a0189637
--- /dev/null
+++ b/py/aoc2023/day14.py
@@ -0,0 +1,76 @@
+"""
+Day 14: Parabolic Reflector Dish
+"""
+
+from itertools import islice
+
+SAMPLE_INPUT = """
+O....#....
+O.OO#....#
+.....##...
+OO.#O....O
+.O.....O#.
+O.#..O.#.#
+..O..#O..O
+.......O..
+#....###..
+#OO..#....
+"""
+
+
+def _tilt(data):
+    data = list(map(list, data))
+    for x in range(max(map(len, data))):
+        y0 = 0
+        while y0 < len(data):
+            n, y1 = 0, y0
+            while y1 < len(data):
+                c = data[y1][x]
+                if c == "O":
+                    n += 1
+                elif c == "#":
+                    break
+                y1 += 1
+            for y in range(y0, y1):
+                data[y][x] = "O" if y < y0 + n else "."
+            y0 = y1 + 1
+    return data
+
+
+def _spin(data):
+    for _ in range(3):
+        data = list(zip(*_tilt(data)[::-1]))
+    return tuple(map("".join, zip(*_tilt(data)[::-1])))
+
+
+def _load(data):
+    return sum((len(line) - i) * line.count("O") for i, line in enumerate(data))
+
+
+def part1(data):
+    """
+    >>> part1(SAMPLE_INPUT)
+    136
+    """
+    return _load(_tilt(filter(None, data.splitlines())))
+
+
+def part2(data):
+    """
+    >>> part2(SAMPLE_INPUT)
+    64
+    """
+    n = 1000000000
+    data = tuple(filter(None, data.splitlines()))
+    cache = {data: 0}
+    for i in range(1, n + 1):
+        data = _spin(data)
+        if data in cache:
+            j = cache[data]
+            data = next(islice(cache.keys(), j + (n - i) % (i - j), None))
+            break
+        cache[data] = i
+    return _load(data)
+
+
+parts = (part1, part2)
diff --git a/py/pyproject.toml b/py/pyproject.toml
index f5490fe4..2fe8bf3d 100644
--- a/py/pyproject.toml
+++ b/py/pyproject.toml
@@ -35,6 +35,7 @@ day10 = "aoc2023.day10:parts"
 day11 = "aoc2023.day11:parts"
 day12 = "aoc2023.day12:parts"
 day13 = "aoc2023.day13:parts"
+day14 = "aoc2023.day14:parts"
 
 [tool.black]
 target_version = ["py312"]