Advent of Code: Day 19, 2016

N_ELVES = 3018458

class Elf():
    n = 0
    def __init__(self, right=None):
        self.left = None
        self.right = right
        Elf.n += 1
        self.n = Elf.n

    def remove_self(self):
        self.left.right = self.right
        self.right.left = self.left
        return self.left # return elf to left for easy iterating

def do_stuff(*args, part_two=False):
    # Create all of the elves and link them together
    Elf.n = 0
    first_elf = Elf()
    last_elf = first_elf
    for i in range(N_ELVES - 1):
        new_elf = Elf(right=last_elf)
        last_elf.left = new_elf
        last_elf = new_elf
    last_elf.left = first_elf
    total_elves = N_ELVES

    # Find first elf that is removed from the game
    current_elf = first_elf
    if part_two:
        for _ in range(N_ELVES // 2):
            current_elf = current_elf.left
    else:
        current_elf = current_elf.left

    # Take one elf out of the game at a time
    while total_elves > 1:
        if part_two:
            current_elf = current_elf.remove_self()
            if total_elves % 2 == 1:
                current_elf = current_elf.left
        else:
            current_elf = current_elf.remove_self().left
        total_elves -= 1

    # Show the remaining elf
    print("Part {}:".format(2 if part_two else 1), current_elf.n)

do_stuff()
do_stuff(part_two=True)