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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
1 changed files with 36 additions and 31 deletions
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59
src/day12.rs
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@@ -18,26 +18,28 @@ impl From<&[u8]> for Farm {
impl Farm { impl Farm {
fn compute_region(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) { fn compute_region(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) {
let our_plant = self.map.get(pos).unwrap(); let our_plant = self.map.get(pos).unwrap();
let mut perimeter = 0;
let mut area = 1;
visited.set(pos, true); visited.set(pos, true);
for adj in [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)].map(|ofs| pos + ofs) { [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)]
match self.map.get(&adj) { .map(|ofs| pos + ofs)
.iter()
.fold((1, 0), |(area, perimeter), adj| {
match self.map.get(adj) {
Some(plant) if plant == our_plant => { Some(plant) if plant == our_plant => {
if visited.get(&adj) == Some(false) { if visited.get(adj) == Some(false) {
// add the perimeter of the growth from there if not visited yet // add the perimeter of the growth from there if not visited yet
let (n_area, n_perimeter) = self.compute_region(&adj, visited); let (add_area, add_perimeter) = self.compute_region(&adj, visited);
area += n_area; (area + add_area, perimeter + add_perimeter)
perimeter += n_perimeter; } else {
}
}
Some(_) | None => perimeter += 1,
}
}
(area, perimeter) (area, perimeter)
} }
}
Some(_) | None => (area, perimeter + 1),
}
})
}
fn regions_cost(&self) -> u64 { fn regions_cost(&self) -> u64 {
let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false); let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false);
let mut cost = 0; let mut cost = 0;
@@ -61,9 +63,10 @@ impl Farm {
cost cost
} }
fn count_corners(&self, pos: &Coord2d) -> u64 { fn count_corners(&self, pos: &Coord2d) -> u64 {
// A // NOTE: Iterating twice is faster than combining conditions in one pass
// AAA has 4 inside corners (pos at centre). check that AA A's exist and B doesn't for each rotation // BAB
// A AB // 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 our_plant = self.map.get(pos);
let inside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)] let inside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)]
.iter() .iter()
@@ -73,6 +76,9 @@ impl Farm {
&& self.map.get(&(pos + (0, inside_corner.1))) == our_plant && self.map.get(&(pos + (0, inside_corner.1))) == our_plant
}) })
.count(); .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)] let outside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)]
.iter() .iter()
.filter(|outside_corner| { .filter(|outside_corner| {
@@ -84,25 +90,24 @@ impl Farm {
} }
fn region_corners(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) { fn region_corners(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) {
let our_plant = self.map.get(pos).unwrap(); let our_plant = self.map.get(pos).unwrap();
let mut area = 1;
let mut corners = self.count_corners(pos);
visited.set(pos, true); visited.set(pos, true);
for adj in [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)].map(|ofs| pos + ofs) { [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)]
match self.map.get(&adj) { .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 => { Some(plant) if plant == our_plant => {
if visited.get(&adj) == Some(false) { if visited.get(adj) == Some(false) {
// add the perimeter of the growth from there if not visited yet // add the perimeter of the growth from there if not visited yet
let (n_area, n_corners) = self.region_corners(&adj, visited); let (n_area, n_corners) = self.region_corners(&adj, visited);
area += n_area; (area+n_area, corners+n_corners)
corners += n_corners; } else { (area, corners) }
} }
Some(_) | None => { (area, corners) }
} }
Some(_) | None => {} })
}
}
(area, corners)
} }
fn regions_discount_cost(&self) -> u64 { fn regions_discount_cost(&self) -> u64 {
let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false); let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false);