var input =File.ReadAllText("input.txt").Split(' ').Select(long.Parse).ToList();
var part1   = GetStonesAfterIteration(25, new List<long>(input)).Values.Sum().ToString();
var part2   = GetStonesAfterIteration(75, new List<long>(input)).Values.Sum().ToString();

Console.WriteLine($"Part1: {part1}\nPart2: {part2}");

Dictionary<long, long> GetStonesAfterIteration(int iteration, List<long> input)
{
    var stones = input.ToDictionary(x => x, x => input.LongCount(y => y == x));
    stones.TryAdd(1, 0);

    for (var i = 0; i < iteration; i++)
    {
        var modifications = new Dictionary<long, long> { { 1, 0 } };
        foreach (var stone in stones)
        {
            if (stone.Key == 0)
            {
                AddStone(1, stone.Value, modifications);
            }
            else if (stone.Key.ToString().Length % 2 == 0)
            {
                var stoneString = stone.Key.ToString();
                var leftStone = int.Parse(stoneString[..(stoneString.Length / 2)]);
                var rightStone = int.Parse(stoneString[(stoneString.Length / 2)..]);

                AddStone(leftStone, stone.Value, modifications);
                AddStone(rightStone, stone.Value, modifications);
            }
            else
            {
                AddStone(stone.Key * 2024, stone.Value, modifications);
            }

            stones.Remove(stone.Key);
        }

        foreach (var modification in modifications) stones[modification.Key] = modification.Value;

        modifications.Clear();
    }

    return stones.Where(x => x.Value > 0).ToDictionary(x => x.Key, x => x.Value);
}

void AddStone(long key, long value, Dictionary<long, long> modifications)
{
    if (!modifications.TryAdd(key, value)) modifications[key] += value;
}