jonas.tngl.sh
Advent of Code solutions in Rust
fix: avoid underflow in vector arithmetic in day 11, 2020
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-14
aoc_2020/src/day11.rs
+14
-14
aoc_2020/src/day11.rs
···
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use itertools::Itertools;
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pub(crate) struct Door {
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seats: HashSet<Vector<usize, 2>>,
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seats: HashSet<Vector<isize, 2>>,
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}
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impl<'input> Solution<'input> for Door {
···
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line.bytes()
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.enumerate()
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.filter(|&(_, b)| b == b'L')
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.map(move |(col, _)| Vector([row, col]))
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.map(move |(col, _)| Vector([row as isize, col as isize]))
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})
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.collect();
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Door { seats }
···
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trait SeatPolicy {
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const THRESHOLD: usize;
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fn neighbors(&self, seat: Vector<usize, 2>) -> impl Iterator<Item = Vector<usize, 2>>;
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fn neighbors(&self, seat: Vector<isize, 2>) -> impl Iterator<Item = Vector<isize, 2>>;
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}
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struct DirectNeighborSeatPolicy;
···
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impl SeatPolicy for DirectNeighborSeatPolicy {
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const THRESHOLD: usize = 4;
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fn neighbors(&self, seat: Vector<usize, 2>) -> impl Iterator<Item = Vector<usize, 2>> {
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fn neighbors(&self, seat: Vector<isize, 2>) -> impl Iterator<Item = Vector<isize, 2>> {
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seat.neighbors()
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}
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}
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struct SightlineSeatPolicy<'s> {
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seats: &'s HashSet<Vector<usize, 2>>,
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bounds: [RangeInclusive<usize>; 2],
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seats: &'s HashSet<Vector<isize, 2>>,
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bounds: [RangeInclusive<isize>; 2],
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}
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impl<'s> SightlineSeatPolicy<'s> {
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fn new(seats: &'s HashSet<Vector<usize, 2>>) -> Self {
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fn new(seats: &'s HashSet<Vector<isize, 2>>) -> Self {
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Self {
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seats,
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bounds: array::from_fn(|i| 0..=seats.iter().map(|s| s[i]).max().unwrap_or(0)),
···
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impl SeatPolicy for SightlineSeatPolicy<'_> {
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const THRESHOLD: usize = 5;
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fn neighbors(&self, seat: Vector<usize, 2>) -> impl Iterator<Item = Vector<usize, 2>> {
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fn neighbors(&self, seat: Vector<isize, 2>) -> impl Iterator<Item = Vector<isize, 2>> {
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seat.neighbors().filter_map(move |neighbor| {
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let dir = neighbor - seat;
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(1..)
···
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}
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fn evolve<P: SeatPolicy>(
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occupied: &HashSet<Vector<usize, 2>>,
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seats: &HashSet<Vector<usize, 2>>,
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occupied: &HashSet<Vector<isize, 2>>,
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seats: &HashSet<Vector<isize, 2>>,
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policy: &P,
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) -> HashSet<Vector<usize, 2>> {
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) -> HashSet<Vector<isize, 2>> {
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let empty = seats.difference(occupied);
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empty
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.copied()
···
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}
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fn fixed_point_occupancy(
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seats: &HashSet<Vector<usize, 2>>,
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seats: &HashSet<Vector<isize, 2>>,
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policy: &impl SeatPolicy,
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) -> HashSet<Vector<usize, 2>> {
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) -> HashSet<Vector<isize, 2>> {
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itertools::iterate(HashSet::new(), |prev| evolve(prev, seats, policy))
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.tuple_windows()
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.find(|(lhs, rhs)| lhs == rhs)
···
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L.LLLLLL.L
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L.LLLLL.LL";
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const EXAMPLE_SEATS: [Vector<usize, 2>; 71] = [
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const EXAMPLE_SEATS: [Vector<isize, 2>; 71] = [
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Vector([0, 0]),
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Vector([0, 2]),
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Vector([0, 3]),