52 lines
1.1 KiB
Rust
52 lines
1.1 KiB
Rust
#![feature(test)]
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use rustc_hash::FxHashMap;
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type Input = Vec<u64>;
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fn setup(input: &str) -> Input {
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input
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.split_whitespace()
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.map(|n| n.parse().unwrap())
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.collect()
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}
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fn solve(input: &Input, steps: usize) -> usize {
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let mut nums = FxHashMap::default();
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let mut new_nums = FxHashMap::default();
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for &n in input {
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*nums.entry(n).or_default() += 1;
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}
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for _ in 0..steps {
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new_nums.clear();
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for (&n, &cnt) in &nums {
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let mut insert = |n| *new_nums.entry(n).or_default() += cnt;
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if n == 0 {
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insert(1);
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continue;
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}
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let d = n.ilog10() + 1;
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if d & 1 == 0 {
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let m = 10u64.pow(d >> 1);
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insert(n / m);
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insert(n % m);
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} else {
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insert(n * 2024);
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}
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}
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std::mem::swap(&mut nums, &mut new_nums);
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}
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nums.values().sum()
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}
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fn part1(input: &Input) -> usize {
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solve(input, 25)
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}
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fn part2(input: &Input) -> usize {
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solve(input, 75)
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}
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aoc::main!(2024, 11, ex: 1);
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