From 696dbfc7390031cf0b4ed8e6044742a61f10628b Mon Sep 17 00:00:00 2001
From: Alfred Melch <dev@melch.pro>
Date: Wed, 23 Dec 2020 17:27:16 +0100
Subject: [PATCH] Solve 2020/23

---
 2020/23/solution1.py |  52 ++++++++++++++++++++++
 2020/23/solution2.py | 102 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 154 insertions(+)
 create mode 100644 2020/23/solution1.py
 create mode 100644 2020/23/solution2.py

diff --git a/2020/23/solution1.py b/2020/23/solution1.py
new file mode 100644
index 0000000..d710b8e
--- /dev/null
+++ b/2020/23/solution1.py
@@ -0,0 +1,52 @@
+"""Solution to 2020/23"""
+
+from collections import deque
+
+EXAMPLE = '389125467'
+INPUT = '952316487'
+
+# INPUT = EXAMPLE
+
+MOVES = 100
+
+
+def main():
+    all_cups = deque(sorted(INPUT))
+    cups = deque(INPUT)
+
+    for move in range(MOVES):
+        print(f'-- MOVE {move + 1} --')
+        while all_cups[0] != cups[0]:
+            all_cups.rotate()
+        print(f'cups: {list(cups)}')
+        cur = cups[0]
+
+        cups.rotate(-1)
+        lift = [cups.popleft(), cups.popleft(), cups.popleft()]
+        next_cup = cups[0]
+        print('pick up:', lift)
+
+        all_cups.rotate()
+        while all_cups[0] in lift:
+            all_cups.rotate()
+        destination = all_cups[0]
+        print('destination:', destination)
+
+        while cups[-1] != destination:
+            cups.rotate()
+        cups.extend(lift)
+
+        while cups[0] != next_cup:
+            cups.rotate()
+
+    print('-- Final:--')
+    print(cups)
+    print()
+
+    while cups[0] != '1':
+        cups.rotate()
+    cups.popleft()
+    print(''.join(list(cups)))
+
+
+main()
diff --git a/2020/23/solution2.py b/2020/23/solution2.py
new file mode 100644
index 0000000..ad1da44
--- /dev/null
+++ b/2020/23/solution2.py
@@ -0,0 +1,102 @@
+"""Solution to 2020/23"""
+
+from collections import deque
+
+EXAMPLE = '389125467'
+INPUT = '952316487'
+
+# INPUT = EXAMPLE
+
+MOVES = 10_000_000
+
+INPUT = list(map(int, INPUT))
+INPUT = INPUT + list(range(max(INPUT) + 1, 1_000_000 + 1))
+
+
+def main():
+    cups = CrabCups(INPUT)
+    print(cups)
+
+    for move in range(MOVES):
+        if move % 1_000_000 == 0:
+            print(f'-- MOVE {move} --')
+        cups.move()
+
+    print()
+    print('finished')
+    print(cups._nodes[1].next.value * cups._nodes[1].next.next.value)
+
+    exit()
+
+
+class CrabCups:
+    def __init__(self, cups):
+        nodes = dict()
+        i = 0
+        prev = None
+        while i < len(cups):
+            node = Node(cups[i])
+            if prev:
+                node.prev = prev
+                prev.next = node
+            prev = node
+            nodes[cups[i]] = node
+            i += 1
+        nodes[cups[0]].prev = nodes[cups[-1]]
+        nodes[cups[-1]].next = nodes[cups[0]]
+        self._nodes = nodes
+        self.cur = nodes[cups[0]]
+        self.cup_count = len(cups)
+        self.last_cur = None
+        self.last_pick_up = None
+        self.last_destination = None
+
+    def move(self):
+        pick_up = set()
+        link = self.cur
+        self.last_cur = self.cur
+        self.last_pick_up = link.next
+        for _ in range(3):
+            link = link.next
+            pick_up.add(link.value)
+
+        # wire cur with cup after pickups
+        link.next.prev = self.cur
+        self.cur.next = link.next
+
+        # find dest
+        dest = self.cur.value - 1
+        dest = dest if dest != 0 else self.cup_count
+        while dest in pick_up:
+            dest -= 1
+            dest = dest if dest != 0 else self.cup_count
+        dest = self._nodes[dest]
+        self.last_dest = dest
+
+        dest.next.prev = link
+        link.next = dest.next
+
+        link = link.prev.prev
+        dest.next = link
+        link.prev = dest
+
+        self.cur = self.cur.next
+
+    def as_list(self, start):
+        cups = [start.value]
+        cur = start.next
+        while not cur is start:
+            cups.append(cur.value)
+            cur = cur.next
+        return cups
+
+
+class Node:
+    next = None
+    prev = None
+
+    def __init__(self, val):
+        self.value = val
+
+
+main()