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Avoid 2/3 hashmap lookups

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Bert Peters
2021-12-20 18:24:37 +01:00
parent aee25057d6
commit 61fb240622
1 changed files with 13 additions and 11 deletions
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12
2021/src/day20.rs
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@@ -39,27 +39,29 @@ fn find_dimensions(field: &Field) -> ((i32, i32), (i32, i32)) {
}
fn advance(translation: &Translation, field: &Field, new_field: &mut Field, infinity: &mut bool) {
const INDEX_MASK: usize = (1 << 9) - 1;
new_field.clear();
let ((xmin, xmax), (ymin, ymax)) = find_dimensions(field);
for x in (xmin - 1)..=(xmax + 1) {
let mut index = if *infinity { INDEX_MASK } else { 0 };
for y in (ymin - 1)..=(ymax + 1) {
let mut index = 0;
for dy in -1..=1 {
for dx in -1..=1 {
index <<= 1;
let nx = x + dx;
let ny = y + dy;
let ny = y + 1;
if nx < xmin || nx > xmax || ny < ymin || ny > ymax {
index |= *infinity as usize;
} else if field.contains(&(x + dx, y + dy)) {
} else if field.contains(&(nx, ny)) {
index |= 1;
}
}
}
index &= INDEX_MASK;
if translation[index] {
new_field.insert((x, y));