71 lines
1.6 KiB
Rust
71 lines
1.6 KiB
Rust
#![feature(test)]
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use aoc::grid::Direction;
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use rustc_hash::FxHashSet;
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type Input = Vec<Motion>;
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#[derive(Debug)]
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struct Motion {
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direction: Direction,
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count: u32,
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}
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struct Solver<'a> {
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motions: &'a [Motion],
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knots: Vec<(isize, isize)>,
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visited: FxHashSet<(isize, isize)>,
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}
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impl<'a> Solver<'a> {
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fn new(input: &'a Input, n: usize) -> Self {
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Self {
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motions: input,
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knots: vec![(0, 0); n],
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visited: FxHashSet::default(),
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}
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}
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fn follow(&mut self, i: usize) {
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let p = self.knots[i - 1].0 - self.knots[i].0;
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let q = self.knots[i - 1].1 - self.knots[i].1;
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if p.abs() > 1 || q.abs() > 1 {
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self.knots[i] = (
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self.knots[i].0 + p.clamp(-1, 1),
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self.knots[i].1 + q.clamp(-1, 1),
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);
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}
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}
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fn solve(mut self) -> usize {
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for Motion { direction, count } in self.motions {
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for _ in 0..*count {
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self.knots[0] = direction.step_signed(self.knots[0]);
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(1..self.knots.len()).for_each(|i| self.follow(i));
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self.visited.insert(*self.knots.last().unwrap());
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}
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}
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self.visited.len()
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}
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}
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fn setup(input: &str) -> Input {
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input
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.trim()
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.lines()
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.map(|line| Motion {
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direction: line.chars().next().unwrap().into(),
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count: line[2..].parse().unwrap(),
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})
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.collect()
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}
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fn part1(input: &Input) -> usize {
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Solver::new(input, 2).solve()
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}
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fn part2(input: &Input) -> usize {
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Solver::new(input, 10).solve()
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}
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aoc::main!(2022, 9, ex: 1, 2);
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