49 lines
1.7 KiB
C#
49 lines
1.7 KiB
C#
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var input =File.ReadAllText("input.txt").Split(' ').Select(long.Parse).ToList();
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var part1 = GetStonesAfterIteration(25, new List<long>(input)).Values.Sum().ToString();
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var part2 = GetStonesAfterIteration(75, new List<long>(input)).Values.Sum().ToString();
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Console.WriteLine($"Part1: {part1}\nPart2: {part2}");
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Dictionary<long, long> GetStonesAfterIteration(int iteration, List<long> input)
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{
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var stones = input.ToDictionary(x => x, x => input.LongCount(y => y == x));
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stones.TryAdd(1, 0);
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for (var i = 0; i < iteration; i++)
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{
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var modifications = new Dictionary<long, long> { { 1, 0 } };
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foreach (var stone in stones)
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{
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if (stone.Key == 0)
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{
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AddStone(1, stone.Value, modifications);
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}
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else if (stone.Key.ToString().Length % 2 == 0)
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{
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var stoneString = stone.Key.ToString();
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var leftStone = int.Parse(stoneString[..(stoneString.Length / 2)]);
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var rightStone = int.Parse(stoneString[(stoneString.Length / 2)..]);
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AddStone(leftStone, stone.Value, modifications);
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AddStone(rightStone, stone.Value, modifications);
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}
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else
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{
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AddStone(stone.Key * 2024, stone.Value, modifications);
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}
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stones.Remove(stone.Key);
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}
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foreach (var modification in modifications) stones[modification.Key] = modification.Value;
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modifications.Clear();
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}
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return stones.Where(x => x.Value > 0).ToDictionary(x => x.Key, x => x.Value);
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}
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void AddStone(long key, long value, Dictionary<long, long> modifications)
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{
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if (!modifications.TryAdd(key, value)) modifications[key] += value;
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}
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