AoC 2024 Day 11 part 2

import re
from collections import defaultdict

with open("day11input.txt") as f:
    input_nums = [int(x) for x in re.findall('\d+', f.read())]

stone_counts = defaultdict(int)
for num in input_nums:
    stone_counts[num] += 1

for _ in range(75):
    new_stone_counts = defaultdict(int)
    for stone, count in stone_counts.items():
        if stone == 0:
            new_stone_counts[1] += count
        elif len(str(stone)) % 2 == 0:
            str_rep = str(stone)
            mid = len(str_rep) // 2
            new_stone_counts[int(str_rep[mid:])] += count
            new_stone_counts[int(str_rep[:mid])] += count
        else:
            new_stone_counts[stone * 2024] += count
    stone_counts = new_stone_counts

print(sum(stone_counts.values()))