from collections import deque class LinkedListNode: def __init__(self, item): self.item = item self.left = None self.right = None my_input = [int(i) for i in "459672813"] def part1(): my_cups = deque(my_input) for _ in range(100): orig = my_cups[0] dest = my_cups[0]-1 if dest < 1: dest = 9 my_cups.rotate(-1) cup1 = my_cups.popleft() cup2 = my_cups.popleft() cup3 = my_cups.popleft() while dest in (cup1, cup2, cup3): dest = dest - 1 if dest > 1 else dest + 8 while my_cups[0] != dest: my_cups.rotate(-1) my_cups.rotate(-1) my_cups.append(cup1) my_cups.append(cup2) my_cups.append(cup3) while my_cups[0] != orig: my_cups.rotate(-1) my_cups.rotate(-1) while my_cups[0] != 1: my_cups.rotate(-1) my_cups.popleft() return ''.join([str(i) for i in my_cups]) print(f"Part 1 solution: {part1()}") 

def part2(): my_nodes = {} last_node = None for i in my_input: curr_node = LinkedListNode(i) my_nodes[i] = curr_node if last_node is not None: last_node.right = curr_node curr_node.left = last_node last_node = curr_node for i in range(len(my_input)+1, 1_000_001): curr_node = LinkedListNode(i) my_nodes[i] = curr_node if last_node is not None: last_node.right = curr_node curr_node.left = last_node last_node = curr_node # Complete the circle  ptr = my_nodes[my_input[0]] last_node.right = ptr ptr.left = last_node ptr = my_nodes[my_input[0]] for i in range(10000000): p_val = ptr.item cup1 = ptr.right cup2 = cup1.right cup3 = cup2.right ptr.right = cup3.right ptr.right.left = ptr d_val = p_val - 1 or 1000000 while d_val in (cup1.item, cup2.item, cup3.item): d_val = d_val - 1 or 1000000 d_node = my_nodes[d_val] cup3.right = d_node.right cup3.right.left = cup3 d_node.right = cup1 cup1.left = d_node ptr = ptr.right while ptr.item != 1: ptr = ptr.right return ptr.right.item * ptr.right.right.item print(f"Part 2 solution: {part2()}")