From bf8d126ee98cd9f9a77bd30fe62e3e020c84f63d Mon Sep 17 00:00:00 2001
From: Sijmen Schoon <me@sijmenschoon.nl>
Date: Fri, 25 Dec 2020 00:23:24 +0100
Subject: [PATCH] python(day23): Day 23

---
 python/day23.py | 75 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 python/day23.py

diff --git a/python/day23.py b/python/day23.py
new file mode 100644
index 0000000..b921395
--- /dev/null
+++ b/python/day23.py
@@ -0,0 +1,75 @@
+import fileinput
+import itertools
+from pprint import pprint
+from typing import Any, Dict, List, Optional, Tuple
+
+
+def parse() -> List[int]:
+    line = next(fileinput.input()).strip()
+    return [int(cup) for cup in line]
+
+
+def step(cups: Dict[int, int], current_label: int, min_, max_) -> int:
+    a = cups[current_label]
+    b = cups[a]
+    c = cups[b]
+    picked_up: List[int] = [a, b, c]
+    cups[current_label] = cups[c]
+
+    destination = current_label - 1
+    if destination < min_:
+        destination = max_
+
+    while destination in picked_up:
+        destination -= 1
+        if destination < min_:
+            destination = max_
+
+    cups[picked_up[2]] = cups[destination]
+    cups[destination] = picked_up[0]
+    return cups[current_label]
+
+
+def part1(labels):
+    cups = [None] * (len(labels) + 1)
+    for i in range(len(labels)):
+        cups[labels[i]] = labels[(i + 1) % len(labels)]
+
+    current = labels[0]
+    min_ = min(labels)
+    max_ = max(labels)
+    for _ in range(100):
+        current = step(cups, current, min_, max_)
+
+    label = 1
+    print("Part 1: ", end="")
+    for _ in range(8):
+        label = cups[label]
+        print(label, end="")
+    print()
+
+def part2(labels):
+    labels = labels + [i for i in range(max(labels) + 1, 1_000_001)]
+    cups = [0] * (len(labels) + 1)
+    for i in range(len(labels)):
+        cups[labels[i]] = labels[(i + 1) % len(labels)]
+
+    current = labels[0]
+    min_ = min(labels)
+    max_ = max(labels)
+    for turn in range(10_000_000):
+        current = step(cups, current, min_, max_)
+
+    a = cups[1]
+    b = cups[a]
+    print("Part 2:", a * b)
+
+
+def main() -> None:
+    labels = parse()
+    part1(labels)
+    part2(labels)
+
+
+if __name__ == "__main__":
+    main()