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[rs] Optimize 2022_12

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This commit is contained in:
Joscha 2022-12-13 10:05:42 +01:00
parent 1dd0c4eaf8
commit 93529c4173
1 changed files with 17 additions and 20 deletions
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37
rs/src/y2022/d12.rs
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@ -93,7 +93,7 @@ impl Step {
}
}
fn neighbours(grid: &Grid<u32>, pos: (i32, i32)) -> Vec<(i32, i32)> {
fn backwards_neighbours(grid: &Grid<u32>, pos: (i32, i32)) -> Vec<(i32, i32)> {
let h = *grid.ati(pos.0, pos.1).unwrap();
let mut result = vec![];
@ -105,7 +105,7 @@ fn neighbours(grid: &Grid<u32>, pos: (i32, i32)) -> Vec<(i32, i32)> {
];
for npos in potential_neighbours {
if let Some(nh) = grid.ati(npos.0, npos.1) {
if *nh <= h + 1 {
if h <= *nh + 1 {
result.push(npos);
}
}
@ -113,8 +113,13 @@ fn neighbours(grid: &Grid<u32>, pos: (i32, i32)) -> Vec<(i32, i32)> {
result
}
fn dijkstra(grid: &Grid<u32>, start: (i32, i32), end: (i32, i32)) -> Grid<Step> {
fn dijkstra<F: Fn((i32, i32), u32) -> bool>(
grid: &Grid<u32>,
start: (i32, i32),
end_f: F,
) -> (Grid<Step>, (i32, i32)) {
let mut steps = Grid::new(grid.width, grid.height, Step::empty());
let mut end = (-1, -1);
let mut heap = BinaryHeap::new();
heap.push(Candidate {
@ -124,16 +129,18 @@ fn dijkstra(grid: &Grid<u32>, start: (i32, i32), end: (i32, i32)) -> Grid<Step>
});
while let Some(Candidate { cost, pos, prev }) = heap.pop() {
let h = *grid.ati(pos.0, pos.1).unwrap();
let mut current = steps.ati_mut(pos.0, pos.1).unwrap();
if pos == end {
if end_f(pos, h) {
current.cost = cost;
current.prev = prev;
end = pos;
break;
} else if cost < current.cost {
current.cost = cost;
current.prev = prev;
for neighbour in neighbours(grid, pos) {
for neighbour in backwards_neighbours(grid, pos) {
heap.push(Candidate {
cost: cost + 1,
pos: neighbour,
@ -143,7 +150,7 @@ fn dijkstra(grid: &Grid<u32>, start: (i32, i32), end: (i32, i32)) -> Grid<Step>
}
}
steps
(steps, end)
}
fn path_length(steps: &Grid<Step>, start: (i32, i32), end: (i32, i32)) -> usize {
@ -186,21 +193,11 @@ pub fn solve(input: String) {
let starti = (start.0 as i32, start.1 as i32);
let endi = (end.0 as i32, end.1 as i32);
let steps = dijkstra(&grid, starti, endi);
let part1 = path_length(&steps, starti, endi);
let (steps, _) = dijkstra(&grid, endi, |p, _| p == starti);
let part1 = path_length(&steps, endi, starti);
println!("Part 1: {part1}");
let mut part2 = usize::MAX;
for y in 0..grid.height {
for x in 0..grid.width {
if *grid.at(x, y).unwrap() == 0 {
let starti = (x as i32, y as i32);
let endi = (end.0 as i32, end.1 as i32);
let steps = dijkstra(&grid, starti, endi);
let length = path_length(&steps, starti, endi);
part2 = part2.min(length);
}
}
}
let (steps, starti) = dijkstra(&grid, endi, |_, h| h == 0);
let part2 = path_length(&steps, endi, starti);
println!("Part 2: {part2}");
}