From 573b17af92045ed8c768defa2fb25f78cb26e722 Mon Sep 17 00:00:00 2001
From: pareronia <49491686+pareronia@users.noreply.github.com>
Date: Fri, 8 Dec 2023 07:23:30 +0100
Subject: [PATCH] AoC 2023 Day 8 Part 2

---
 README.md                     |  2 +-
 src/main/python/AoC2023_08.py | 39 ++++++++++++++++++++++++++---------
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/README.md b/README.md
index a28d0014..adcdcb2e 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@
 <!-- @BEGIN:ImplementationsTable:2023@ -->
 | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 |
 | ---| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
-| python3 | [✓](src/main/python/AoC2023_01.py) | [✓](src/main/python/AoC2023_02.py) | [✓](src/main/python/AoC2023_03.py) | [✓](src/main/python/AoC2023_04.py) | [✓](src/main/python/AoC2023_05.py) | [✓](src/main/python/AoC2023_06.py) | [✓](src/main/python/AoC2023_07.py) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+| python3 | [✓](src/main/python/AoC2023_01.py) | [✓](src/main/python/AoC2023_02.py) | [✓](src/main/python/AoC2023_03.py) | [✓](src/main/python/AoC2023_04.py) | [✓](src/main/python/AoC2023_05.py) | [✓](src/main/python/AoC2023_06.py) | [✓](src/main/python/AoC2023_07.py) | [✓](src/main/python/AoC2023_08.py) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
 | java | [✓](src/main/java/AoC2023_01.java) | [✓](src/main/java/AoC2023_02.java) | [✓](src/main/java/AoC2023_03.java) | [✓](src/main/java/AoC2023_04.java) |  | [✓](src/main/java/AoC2023_06.java) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
 | bash |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
 | c++ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
diff --git a/src/main/python/AoC2023_08.py b/src/main/python/AoC2023_08.py
index 1f77fd62..f25decda 100644
--- a/src/main/python/AoC2023_08.py
+++ b/src/main/python/AoC2023_08.py
@@ -3,16 +3,15 @@
 # Advent of Code 2023 Day 8
 #
 
+import itertools
 import sys
+from math import lcm
 from typing import NamedTuple
-import itertools
 
 from aoc import my_aocd
 from aoc.common import InputData
 from aoc.common import SolutionBase
 from aoc.common import aoc_samples
-# from aoc.common import log
-
 
 TEST1 = """\
 RL
@@ -32,6 +31,18 @@
 BBB = (AAA, ZZZ)
 ZZZ = (ZZZ, ZZZ)
 """
+TEST3 = """\
+LR
+
+11A = (11B, XXX)
+11B = (XXX, 11Z)
+11Z = (11B, XXX)
+22A = (22B, XXX)
+22B = (22C, 22C)
+22C = (22Z, 22Z)
+22Z = (22B, 22B)
+XXX = (XXX, XXX)
+"""
 
 
 class Map(NamedTuple):
@@ -55,27 +66,35 @@ def parse_input(self, input_data: InputData) -> Map:
         map = Map(instructions, network)
         return map
 
-    def part_1(self, map: Map) -> Output1:
+    def _steps(self, map: Map, start_key: str) -> int:
         inss = itertools.cycle(map.instructions)
-        node = map.network['AAA']
+        node = map.network[start_key]
         ans = 1
         while True:
             ins = next(inss)
-            key = node[0 if ins == 'L' else 1]
-            if key == 'ZZZ':
+            key = node[0 if ins == "L" else 1]
+            if key[-1] == "Z":
                 break
             node = map.network[key]
             ans += 1
         return ans
 
-    def part_2(self, input: Map) -> Output2:
-        return 0
+    def part_1(self, map: Map) -> Output1:
+        return self._steps(map, "AAA")
+
+    def part_2(self, map: Map) -> Output2:
+        keys = [k for k in map.network if k[-1] == "A"]
+        steps = [self._steps(map, key) for key in keys]
+        ans = steps[0]
+        for s in steps[1:]:
+            ans = lcm(ans, s)
+        return ans
 
     @aoc_samples(
         (
             ("part_1", TEST1, 2),
             ("part_1", TEST2, 6),
-            # ("part_2", TEST, "TODO"),
+            ("part_2", TEST3, 6),
         )
     )
     def samples(self) -> None: