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Compute all required points at once

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This commit is contained in:
Bert Peters
2023-12-21 21:48:06 +01:00
parent ca054363bf
commit a891d08b21
1 changed files with 30 additions and 20 deletions
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50
2023/src/day21.rs
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@@ -52,7 +52,10 @@ pub fn part1(input: &[u8]) -> anyhow::Result<String> {
part1_parametrized(input, 64) part1_parametrized(input, 64)
} }
fn compute_infinimap(input: &[u8], steps: i64) -> anyhow::Result<i64> { fn compute_infinimap<const L: usize>(
input: &[u8],
steps_groups: [i64; L],
) -> anyhow::Result<[i64; L]> {
let map = Grid::new(input)?; let map = Grid::new(input)?;
let width = map.width() as i64; let width = map.width() as i64;
let height = map.height() as i64; let height = map.height() as i64;
@@ -64,11 +67,17 @@ fn compute_infinimap(input: &[u8], steps: i64) -> anyhow::Result<i64> {
let mut todo = VecDeque::new(); let mut todo = VecDeque::new();
todo.push_back((0, (start.0 as i64, start.1 as i64))); todo.push_back((0, (start.0 as i64, start.1 as i64)));
let mut count = (steps + 1) % 2; let mut final_counts = [0; L];
let mut counts = [1, 0];
let mut i = 0;
while let Some((dist, (x, y))) = todo.pop_front() { while let Some((dist, (x, y))) = todo.pop_front() {
if dist == steps { if dist == steps_groups[i] {
break; final_counts[i] = counts[(steps_groups[i] % 2) as usize];
i += 1;
if i >= steps_groups.len() {
break;
}
} }
let mut enqueue = |x, y| { let mut enqueue = |x, y| {
let map_x = (((x % width) + width) % width) as usize; let map_x = (((x % width) + width) % width) as usize;
@@ -77,9 +86,7 @@ fn compute_infinimap(input: &[u8], steps: i64) -> anyhow::Result<i64> {
if map[(map_y, map_x)] != b'#' && visited.insert((x, y)) { if map[(map_y, map_x)] != b'#' && visited.insert((x, y)) {
todo.push_back((dist + 1, (x, y))); todo.push_back((dist + 1, (x, y)));
if (dist + 1) % 2 == steps % 2 { counts[((dist + 1) % 2) as usize] += 1;
count += 1;
}
} }
}; };
@@ -89,7 +96,7 @@ fn compute_infinimap(input: &[u8], steps: i64) -> anyhow::Result<i64> {
enqueue(x, y + 1); enqueue(x, y + 1);
} }
Ok(count) Ok(final_counts)
} }
// 616665063284297 too high // 616665063284297 too high
@@ -97,10 +104,7 @@ pub fn part2(input: &[u8]) -> anyhow::Result<String> {
// This is wrong for things that aren't the input but it works for me, so… // This is wrong for things that aren't the input but it works for me, so…
let dests = [65, 65 + 131, 65 + 2 * 131]; let dests = [65, 65 + 131, 65 + 2 * 131];
let mut counts = [0; 3]; let counts = compute_infinimap(input, dests)?;
for (steps, count) in dests.into_iter().zip(&mut counts) {
*count = compute_infinimap(input, steps)?;
}
// Stolen set of equations, this fits a quadratic equation to a three points at x = 0, 1, 2 // Stolen set of equations, this fits a quadratic equation to a three points at x = 0, 1, 2
let a = 0; let a = 0;
@@ -148,13 +152,19 @@ mod tests {
#[test] #[test]
fn sample_infinimap() { fn sample_infinimap() {
assert_eq!(16, compute_infinimap(SAMPLE, 6).unwrap()); let inputs = [
assert_eq!(50, compute_infinimap(SAMPLE, 10).unwrap()); 6, 10, 50, 100,
assert_eq!(1594, compute_infinimap(SAMPLE, 50).unwrap()); // 500
assert_eq!(6536, compute_infinimap(SAMPLE, 100).unwrap()); // 1000
// Commented out because they take forever but they should work. // 5000
// assert_eq!(167004, compute_infinimap(SAMPLE, 500).unwrap()); ];
// assert_eq!(668697, compute_infinimap(SAMPLE, 1000).unwrap()); let expected = [
// assert_eq!(16733044, compute_infinimap(SAMPLE, 5000).unwrap()); 16, 50, 1594, 6536,
// 167004,
// 668697,
// 16733044,
];
assert_eq!(expected, compute_infinimap(SAMPLE, inputs).unwrap());
} }
} }