354 lines
9.1 KiB
Rust
354 lines
9.1 KiB
Rust
use aoc_runner_derive::{aoc, aoc_generator};
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#[derive(Debug)]
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struct Path {
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path: [Option<DirButton>; 6],
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}
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impl Path {
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const fn from(buttons: &[DirButton]) -> Option<Self> {
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let steps = buttons.len();
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let mut path = [None, None, None, None, None, None];
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let mut i = 0;
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while i < steps {
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path[i] = Some(buttons[i]);
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i += 1;
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}
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path[i] = Some(DirButton::A);
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Some(Self { path })
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}
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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enum DirButton {
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Up,
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Down,
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Left,
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Right,
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A,
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}
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const DIRBUTTON_PATHS: [[[Option<Path>; 2]; 5]; 5] = [
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// Up
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[
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// Up
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[Path::from(&[]), None],
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// Down
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[Path::from(&[DirButton::Down]), None],
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// Left
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[Path::from(&[DirButton::Down, DirButton::Left]), None],
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// Right
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[
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Path::from(&[DirButton::Down, DirButton::Right]),
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Path::from(&[DirButton::Right, DirButton::Down]),
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],
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// A
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[Path::from(&[DirButton::Right]), None],
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],
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// Down
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[
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// Up
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[Path::from(&[DirButton::Up]), None],
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// Down
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[Path::from(&[]), None],
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// Left
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[Path::from(&[DirButton::Left]), None],
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// Right
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[Path::from(&[DirButton::Right]), None],
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// A
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[
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Path::from(&[DirButton::Up, DirButton::Right]),
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Path::from(&[DirButton::Right, DirButton::Up]),
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],
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],
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// Left
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[
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// Up
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[Path::from(&[DirButton::Right, DirButton::Up]), None],
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// Down
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[Path::from(&[DirButton::Right]), None],
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// Left
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[Path::from(&[]), None],
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// Right
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[Path::from(&[DirButton::Right, DirButton::Right]), None],
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// A
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[
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Path::from(&[DirButton::Right, DirButton::Right, DirButton::Up]),
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None,
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],
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],
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// Right
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[
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// Up
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[
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Path::from(&[DirButton::Up, DirButton::Left]),
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Path::from(&[DirButton::Left, DirButton::Up]),
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],
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// Down
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[Path::from(&[DirButton::Left]), None],
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// Left
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[Path::from(&[DirButton::Left, DirButton::Left]), None],
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// Right
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[Path::from(&[]), None],
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// A
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[Path::from(&[DirButton::Up]), None],
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],
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// A
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[
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// Up
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[Path::from(&[DirButton::Left]), None],
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// Down
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[
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Path::from(&[DirButton::Down, DirButton::Left]),
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Path::from(&[DirButton::Left, DirButton::Down]),
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],
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// Left
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[
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Path::from(&[DirButton::Down, DirButton::Left, DirButton::Left]),
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None,
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],
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// Right
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[Path::from(&[DirButton::Down]), None],
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// A
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[Path::from(&[]), None],
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],
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];
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impl DirButton {
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const fn index(&self) -> usize {
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match self {
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DirButton::Up => 0,
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DirButton::Down => 1,
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DirButton::Left => 2,
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DirButton::Right => 3,
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DirButton::A => 4,
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}
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}
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const fn paths_to(&self, other: &DirButton) -> &[Option<Path>; 2] {
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&DIRBUTTON_PATHS[self.index()][other.index()]
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}
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}
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#[derive(Debug, PartialEq, Eq)]
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enum NumButton {
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One,
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Two,
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Three,
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Four,
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Five,
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Six,
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Seven,
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Eight,
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Nine,
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Zero,
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A,
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}
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impl NumButton {
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const fn pos(&self) -> (usize, usize) {
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match self {
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NumButton::One => (0, 2),
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NumButton::Two => (1, 2),
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NumButton::Three => (2, 2),
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NumButton::Four => (0, 1),
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NumButton::Five => (1, 1),
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NumButton::Six => (2, 1),
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NumButton::Seven => (0, 0),
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NumButton::Eight => (1, 0),
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NumButton::Nine => (2, 0),
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NumButton::Zero => (1, 3),
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NumButton::A => (2, 3),
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}
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}
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fn paths_to(&self, other: &NumButton) -> [Option<Path>; 2] {
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let start = self.pos();
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let end = other.pos();
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let bx = if start.0 < end.0 {
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DirButton::Right
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} else {
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DirButton::Left
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};
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let dx = start.0.abs_diff(end.0);
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let by = if start.1 < end.1 {
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DirButton::Down
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} else {
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DirButton::Up
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};
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let dy = start.1.abs_diff(end.1);
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if start.0 == 0 && end.1 == 3 {
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let mut x = [None, None, None, None, None, None];
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(0..dx).for_each(|i| {
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x[i] = Some(bx);
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});
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(0..dy).for_each(|i| {
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x[i + dx] = Some(by);
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});
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x[dx + dy] = Some(DirButton::A);
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[Some(Path { path: x }), None]
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} else if end.0 == 0 && start.1 == 3 {
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let mut y = [None, None, None, None, None, None];
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(0..dx).for_each(|i| {
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y[i + dy] = Some(bx);
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});
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(0..dy).for_each(|i| {
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y[i] = Some(by);
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});
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y[dx + dy] = Some(DirButton::A);
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[Some(Path { path: y }), None]
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} else {
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let mut x = [None, None, None, None, None, None];
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let mut y = [None, None, None, None, None, None];
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(0..dx).for_each(|i| {
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x[i] = Some(bx);
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y[i + dy] = Some(bx);
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});
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(0..dy).for_each(|i| {
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x[i + dx] = Some(by);
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y[i] = Some(by);
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});
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x[dx + dy] = Some(DirButton::A);
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y[dx + dy] = Some(DirButton::A);
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[Some(Path { path: x }), Some(Path { path: y })]
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}
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}
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}
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type Input = Vec<(DistanceSize, Vec<NumButton>)>;
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#[aoc_generator(day21)]
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fn parse(input: &str) -> Input {
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input
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.lines()
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.map(|line| {
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(
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line[0..3].parse().unwrap(),
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line.chars()
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.map(|c| match c {
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'1' => NumButton::One,
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'2' => NumButton::Two,
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'3' => NumButton::Three,
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'4' => NumButton::Four,
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'5' => NumButton::Five,
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'6' => NumButton::Six,
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'7' => NumButton::Seven,
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'8' => NumButton::Eight,
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'9' => NumButton::Nine,
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'0' => NumButton::Zero,
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'A' => NumButton::A,
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_ => unreachable!(),
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})
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.collect(),
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)
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})
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.collect()
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}
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type DistanceSize = u64;
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type DistanceMatrix = [[DistanceSize; 5]; 5];
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fn precompute_steps(steps: &mut [DistanceMatrix]) {
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if steps.len() == 1 {
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return;
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}
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precompute_steps(&mut steps[1..]);
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let buttons = [
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DirButton::Up,
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DirButton::Down,
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DirButton::Left,
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DirButton::Right,
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DirButton::A,
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];
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buttons.iter().for_each(|start| {
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buttons.iter().for_each(|end| {
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steps[0][start.index()][end.index()] = start
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.paths_to(end)
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.iter()
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.flatten()
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.map(|path| {
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path.path
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.iter()
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.flatten()
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.fold((0, &DirButton::A), |acc, next| {
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(acc.0 + steps[1][acc.1.index()][next.index()], next)
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})
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.0
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})
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.fold(DistanceSize::MAX, |acc, next| acc.min(next));
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});
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});
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}
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fn shortest_dir_path(path: &Path, steps: &mut [DistanceMatrix]) -> DistanceSize {
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path.path
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.iter()
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.flatten()
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.fold((0, &DirButton::A), |acc, next| {
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(acc.0 + steps[0][acc.1.index()][next.index()], next)
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})
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.0
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}
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fn shortest_path(path: &[NumButton], steps: &mut [DistanceMatrix]) -> DistanceSize {
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path.iter()
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.fold((0, &NumButton::A), |acc, end| {
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(
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acc.0
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+ acc
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.1
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.paths_to(end)
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.iter()
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.flatten()
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.map(|path| shortest_dir_path(path, steps))
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.fold(DistanceSize::MAX, |acc, next| acc.min(next)),
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end,
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)
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})
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.0
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}
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#[aoc(day21, part1)]
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fn part1(input: &Input) -> DistanceSize {
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let mut steps = vec![[[1; 5]; 5]; 3];
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precompute_steps(&mut steps);
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input
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.iter()
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.map(|(num, path)| num * shortest_path(path, &mut steps))
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.sum()
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}
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#[aoc(day21, part2)]
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fn part2(input: &Input) -> DistanceSize {
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let mut steps = vec![[[1; 5]; 5]; 26];
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precompute_steps(&mut steps);
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input
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.iter()
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.map(|(num, path)| num * shortest_path(path, &mut steps))
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.sum()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn part1_example() {
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assert_eq!(part1(&parse("179A")), 68 * 179);
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assert_eq!(part1(&parse("379A")), 64 * 379);
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assert_eq!(part1(&parse("456A")), 64 * 456);
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assert_eq!(part1(&parse("980A")), 60 * 980);
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assert_eq!(part1(&parse("029A")), 68 * 29);
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}
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}
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