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day16: much cleaner, nicely factored solution, and much faster

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This commit is contained in:
Keenan Tims
2023-12-15 23:42:43 -08:00
parent 332620db0f
commit 427a0c766b
1 changed files with 134 additions and 111 deletions
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245
16/src/main.rs
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@@ -28,12 +28,72 @@ fn main() {
// PARSE
enum Interaction {
One(FromDirection),
Two((FromDirection, FromDirection)),
}
#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
enum FromDirection {
Left,
Above,
Right,
Below,
Left = 0,
Above = 1,
Right = 2,
Below = 3,
}
impl FromDirection {
fn mask(&self) -> u8 {
1 << *self as u8
}
// return the new pos for a ray that will be from the direction.
// a ray 'from' left 'goes' right
fn goes_pos(&self, pos: (i64, i64)) -> (i64, i64) {
match self {
Self::Left => (pos.0 + 1, pos.1),
Self::Right => (pos.0 - 1, pos.1),
Self::Above => (pos.0, pos.1 + 1),
Self::Below => (pos.0, pos.1 - 1),
}
}
fn reflect_ne(&self) -> Self {
match self {
Self::Left => Self::Below,
Self::Right => Self::Above,
Self::Above => Self::Right,
Self::Below => Self::Left,
}
}
fn opposite(&self) -> FromDirection {
match self {
Self::Left => Self::Right,
Self::Right => Self::Left,
Self::Above => Self::Below,
Self::Below => Self::Above,
}
}
fn reflect_se(&self) -> FromDirection {
self.reflect_ne().opposite()
}
fn interact(&self, tile: char) -> Interaction {
match tile {
'.' => Interaction::One(*self),
'/' => Interaction::One(self.reflect_ne()),
'\\' => Interaction::One(self.reflect_se()),
'|' => match self {
FromDirection::Above | FromDirection::Below => Interaction::One(*self),
FromDirection::Left | FromDirection::Right => {
Interaction::Two((FromDirection::Above, FromDirection::Below))
}
},
'-' => match self {
FromDirection::Left | FromDirection::Right => Interaction::One(*self),
FromDirection::Above | FromDirection::Below => {
Interaction::Two((FromDirection::Left, FromDirection::Right))
}
},
c => unimplemented!("invalid tile {}", c),
}
}
}
impl Display for FromDirection {
@@ -52,44 +112,55 @@ struct Contraption {
}
struct VisitState {
energized: Vec<Vec<bool>>,
visited_rays: HashSet<((i64, i64), FromDirection)>,
visited_from: Vec<Vec<u8>>,
}
impl VisitState {
fn score(&self) -> u64 {
self.energized.iter().flatten().filter(|c| **c).count() as u64
fn visit(&mut self, pos: (i64, i64), dir: FromDirection) -> bool {
let pos_state = &mut self.visited_from[pos.1 as usize][pos.0 as usize];
if *pos_state & dir.mask() > 0 {
false
} else {
*pos_state |= dir.mask();
true
}
}
fn score(&self) -> u64 {
self.visited_from
.iter()
.flatten()
.filter(|c| **c != 0)
.count() as u64
}
#[allow(dead_code)]
fn dump(&self) {
println!("Score {}:", self.score());
for line in &self.energized {
for line in &self.visited_from {
println!(
" {}",
String::from_iter(line.iter().map(|b| if *b { '#' } else { '.' }))
String::from_iter(line.iter().map(|b| if *b == 0 { '.' } else { '#' }))
);
}
}
}
impl Contraption {
fn cast_ray<'a>(
&'a mut self,
state: &'a mut VisitState,
pos: (i64, i64),
dir: FromDirection,
) {
let mut new_rays = self.cast_ray_inner(state, pos, dir);
loop {
fn height(&self) -> i64 {
self.tiles.len() as i64
}
fn width(&self) -> i64 {
self.tiles[0].len() as i64
}
fn cast_ray<'a>(&'a mut self, pos: (i64, i64), dir: FromDirection) -> VisitState {
let mut state = self.empty_state();
let mut new_rays = self.cast_ray_inner(&mut state, pos, dir);
while new_rays.len() != 0 {
new_rays = new_rays
.iter()
.flat_map(|(pos, dir)| self.cast_ray_inner(state, *pos, *dir))
.flat_map(|(pos, dir)| self.cast_ray_inner(&mut state, *pos, *dir))
.collect();
if new_rays.len() == 0 {
break;
}
}
state
}
fn cast_ray_inner<'a>(
&'a mut self,
@@ -97,68 +168,29 @@ impl Contraption {
mut pos: (i64, i64),
mut dir: FromDirection,
) -> Vec<((i64, i64), FromDirection)> {
let width = state.energized[0].len();
let height = state.energized.len();
let mut new_rays = Vec::new();
while pos.0 >= 0 && pos.1 >= 0 && pos.0 < width as i64 && pos.1 < height as i64 {
// visit pos
state.energized[pos.1 as usize][pos.0 as usize] = true;
if !state.visited_rays.insert((pos, dir)) {
while pos.0 >= 0 && pos.1 >= 0 && pos.0 < self.width() && pos.1 < self.height() {
if !state.visit(pos, dir) {
break;
}
(pos, dir) = match self.tiles[pos.1 as usize][pos.0 as usize] {
'.' => match dir {
FromDirection::Left => ((pos.0 + 1, pos.1), dir),
FromDirection::Right => ((pos.0 - 1, pos.1), dir),
FromDirection::Above => ((pos.0, pos.1 + 1), dir),
FromDirection::Below => ((pos.0, pos.1 - 1), dir),
},
'/' => match dir {
// from left, go up, from below
FromDirection::Left => ((pos.0, pos.1 - 1), FromDirection::Below),
// from up, go left, from the right
FromDirection::Above => ((pos.0 - 1, pos.1), FromDirection::Right),
// from right, go down, from above
FromDirection::Right => ((pos.0, pos.1 + 1), FromDirection::Above),
// from below, go right, from left
FromDirection::Below => ((pos.0 + 1, pos.1), FromDirection::Left),
},
'\\' => match dir {
FromDirection::Left => ((pos.0, pos.1 + 1), FromDirection::Above),
FromDirection::Above => ((pos.0 + 1, pos.1), FromDirection::Left),
FromDirection::Right => ((pos.0, pos.1 - 1), FromDirection::Below),
FromDirection::Below => ((pos.0 - 1, pos.1), FromDirection::Right),
},
'-' => match dir {
FromDirection::Left => ((pos.0 + 1, pos.1), dir),
FromDirection::Right => ((pos.0 - 1, pos.1), dir),
FromDirection::Above | FromDirection::Below => {
new_rays.push(((pos.0 + 1, pos.1), FromDirection::Left));
((pos.0 - 1, pos.1), FromDirection::Right)
}
},
'|' => match dir {
FromDirection::Above => ((pos.0, pos.1 + 1), dir),
FromDirection::Below => ((pos.0, pos.1 - 1), dir),
FromDirection::Left | FromDirection::Right => {
new_rays.push(((pos.0, pos.1 + 1), FromDirection::Above));
((pos.0, pos.1 - 1), FromDirection::Below)
}
},
c => unimplemented!("invalid character {}", c),
}
dir = match dir.interact(self.tiles[pos.1 as usize][pos.0 as usize]) {
Interaction::One(dir) => dir,
Interaction::Two((dir1, dir2)) => {
new_rays.push((pos, dir1));
dir2
}
};
pos = dir.goes_pos(pos);
}
new_rays
}
fn empty_state(&self) -> VisitState {
let mut energized = Vec::new();
for _ in 0..self.tiles.len() {
energized.push(Vec::from_iter(repeat(false).take(self.tiles[0].len())));
}
VisitState {
energized,
visited_rays: HashSet::new(),
let mut visited_from = Vec::new();
for _ in 0..self.height() {
visited_from.push(Vec::from_iter(repeat(0).take(self.width() as usize)));
}
VisitState { visited_from }
}
}
@@ -176,48 +208,39 @@ impl<T: BufRead> From<Lines<T>> for Contraption {
fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
let mut contraption = Contraption::from(input);
let mut state = contraption.empty_state();
contraption.cast_ray(&mut state, (0,0), FromDirection::Left);
state.energized.iter().flatten().filter(|c| **c).count() as u64
contraption.cast_ray((0, 0), FromDirection::Left).score()
}
// PROBLEM 2 solution
fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
let mut contraption = Contraption::from(input);
let mut max_tiles = 0u64;
for y in 0..contraption.tiles.len() as i64 {
let mut left_state = contraption.empty_state();
contraption.cast_ray(&mut left_state, (0, y), FromDirection::Left);
let mut right_state = contraption.empty_state();
contraption.cast_ray(
&mut right_state,
(contraption.tiles[0].len() as i64 - 1, y),
FromDirection::Right,
);
max_tiles = std::cmp::max(
let rows_max = (0..contraption.height()).fold(0, |max_tiles, y| {
std::cmp::max(
max_tiles,
std::cmp::max(left_state.score(), right_state.score()),
);
}
for x in 0..contraption.tiles[0].len() as i64 {
let mut top_state = contraption.empty_state();
contraption.cast_ray(&mut top_state, (x, 0), FromDirection::Above);
let mut bottom_state = contraption.empty_state();
contraption.cast_ray(
&mut bottom_state,
(x, contraption.tiles.len() as i64 - 1),
FromDirection::Below,
);
max_tiles = std::cmp::max(
max_tiles,
std::cmp::max(top_state.score(), bottom_state.score()),
);
}
std::cmp::max(
contraption.cast_ray((0, y), FromDirection::Left).score(),
contraption
.cast_ray((contraption.width() - 1, y), FromDirection::Right)
.score(),
),
)
});
max_tiles
let cols_max = (0..contraption.width()).fold(0, |max_tiles, x| {
std::cmp::max(
max_tiles,
std::cmp::max(
contraption.cast_ray((x, 0), FromDirection::Above).score(),
contraption
.cast_ray((x, contraption.height() - 1), FromDirection::Below)
.score(),
),
)
});
std::cmp::max(rows_max, cols_max)
}
#[cfg(test)]