From 34c57b32b0efcc36bb9a1760a5ebf64b2cbde928 Mon Sep 17 00:00:00 2001
From: Daniel Lin <ephemient@gmail.com>
Date: Wed, 11 Dec 2024 01:54:18 -0500
Subject: [PATCH] Day 11: Plutonian Pebbles

---
 README.md           |  2 +-
 py/aoc2024/day11.py | 42 ++++++++++++++++++++++++++++++++++++++++++
 py/pyproject.toml   |  1 +
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 py/aoc2024/day11.py

diff --git a/README.md b/README.md
index 4ef7297..73a7d6a 100644
--- a/README.md
+++ b/README.md
@@ -15,4 +15,4 @@ Development occurs in language-specific directories:
 |[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.py](py/aoc2024/day10.py)|[day10.rs](rs/src/day10.rs)|
-|[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|||
+|[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|[day11.py](py/aoc2024/day11.py)||
diff --git a/py/aoc2024/day11.py b/py/aoc2024/day11.py
new file mode 100644
index 0000000..1e31a94
--- /dev/null
+++ b/py/aoc2024/day11.py
@@ -0,0 +1,42 @@
+"""
+Day 11: Plutonian Pebbles
+"""
+
+from collections import Counter
+
+
+def part1(data: str) -> int:
+    return _solve(data, 25)
+
+
+def part2(data: str) -> int:
+    return _solve(data, 75)
+
+
+def _solve(data: str, n: int) -> int:
+    """
+    >>> _solve("0 1 10 99 999", 1)
+    7
+    >>> _solve("125 17", 6)
+    22
+    >>> _solve("125 17", 25)
+    55312
+    """
+    counts = Counter(map(int, data.split()))
+    for i in range(n):
+        next = Counter()
+        for num, count in counts.items():
+            if num == 0:
+                next[1] += count
+            else:
+                string = str(num)
+                if len(string) % 2 == 0:
+                    next[int(string[: len(string) // 2])] += count
+                    next[int(string[len(string) // 2 :])] += count
+                else:
+                    next[2024 * num] += count
+        counts = next
+    return counts.total()
+
+
+parts = (part1, part2)
diff --git a/py/pyproject.toml b/py/pyproject.toml
index c67e318..7bfffa4 100644
--- a/py/pyproject.toml
+++ b/py/pyproject.toml
@@ -34,6 +34,7 @@ day7 = "aoc2024.day7:parts"
 day8 = "aoc2024.day8:parts"
 day9 = "aoc2024.day9:parts"
 day10 = "aoc2024.day10:parts"
+day11 = "aoc2024.day11:parts"
 
 [build-system]
 requires = ["poetry-core"]