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day12: optimization and cleanup

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This commit is contained in:
Keenan Tims 2024-12-12 01:24:14 -08:00
parent a56fc933c9
commit c213bbbc27
Signed by: ktims
GPG Key ID: 11230674D69038D4
1 changed files with 36 additions and 31 deletions
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67
src/day12.rs
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@ -18,26 +18,28 @@ impl From<&[u8]> for Farm {
impl Farm {
fn compute_region(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) {
let our_plant = self.map.get(pos).unwrap();
let mut perimeter = 0;
let mut area = 1;
visited.set(pos, true);
for adj in [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)].map(|ofs| pos + ofs) {
match self.map.get(&adj) {
Some(plant) if plant == our_plant => {
if visited.get(&adj) == Some(false) {
// add the perimeter of the growth from there if not visited yet
let (n_area, n_perimeter) = self.compute_region(&adj, visited);
area += n_area;
perimeter += n_perimeter;
[(-1i64, 0i64), (1, 0), (0, -1), (0, 1)]
.map(|ofs| pos + ofs)
.iter()
.fold((1, 0), |(area, perimeter), adj| {
match self.map.get(adj) {
Some(plant) if plant == our_plant => {
if visited.get(adj) == Some(false) {
// add the perimeter of the growth from there if not visited yet
let (add_area, add_perimeter) = self.compute_region(&adj, visited);
(area + add_area, perimeter + add_perimeter)
} else {
(area, perimeter)
}
}
Some(_) | None => (area, perimeter + 1),
}
Some(_) | None => perimeter += 1,
}
}
(area, perimeter)
})
}
fn regions_cost(&self) -> u64 {
let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false);
let mut cost = 0;
@ -61,9 +63,10 @@ impl Farm {
cost
}
fn count_corners(&self, pos: &Coord2d) -> u64 {
// A
// AAA has 4 inside corners (pos at centre). check that AA A's exist and B doesn't for each rotation
// A AB
// NOTE: Iterating twice is faster than combining conditions in one pass
// BAB
// AAA has 4 inside corners (pos at centre). check that for AA A's exist and B doesn't for each rotation
// BAB AB
let our_plant = self.map.get(pos);
let inside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)]
.iter()
@ -73,6 +76,9 @@ impl Farm {
&& self.map.get(&(pos + (0, inside_corner.1))) == our_plant
})
.count();
// BBB
// BAB has 4 outside corners (pos at centre). check that for AB the B are both not equal to A for each rot
// BBB BB B
let outside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)]
.iter()
.filter(|outside_corner| {
@ -84,25 +90,24 @@ impl Farm {
}
fn region_corners(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) {
let our_plant = self.map.get(pos).unwrap();
let mut area = 1;
let mut corners = self.count_corners(pos);
visited.set(pos, true);
for adj in [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)].map(|ofs| pos + ofs) {
match self.map.get(&adj) {
Some(plant) if plant == our_plant => {
if visited.get(&adj) == Some(false) {
// add the perimeter of the growth from there if not visited yet
let (n_area, n_corners) = self.region_corners(&adj, visited);
area += n_area;
corners += n_corners;
[(-1i64, 0i64), (1, 0), (0, -1), (0, 1)]
.map(|ofs| pos + ofs)
.iter()
.fold((1, self.count_corners(pos)), |(area, corners), adj| {
match self.map.get(adj) {
Some(plant) if plant == our_plant => {
if visited.get(adj) == Some(false) {
// add the perimeter of the growth from there if not visited yet
let (n_area, n_corners) = self.region_corners(&adj, visited);
(area+n_area, corners+n_corners)
} else { (area, corners) }
}
Some(_) | None => { (area, corners) }
}
Some(_) | None => {}
}
}
(area, corners)
})
}
fn regions_discount_cost(&self) -> u64 {
let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false);