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Avoid allocations

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Bert Peters
2021-12-20 18:14:36 +01:00
parent a98332894f
commit aee25057d6
1 changed files with 10 additions and 11 deletions
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19
2021/src/day20.rs
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@@ -1,5 +1,6 @@
use std::collections::HashSet;
use std::io::Read;
use std::mem::swap;
type Translation = [bool; 512];
type Point = (i32, i32);
@@ -37,8 +38,8 @@ fn find_dimensions(field: &Field) -> ((i32, i32), (i32, i32)) {
})
}
fn advance(translation: &Translation, field: &Field, infinity: bool) -> (bool, Field) {
let mut new_field = Field::new();
fn advance(translation: &Translation, field: &Field, new_field: &mut Field, infinity: &mut bool) {
new_field.clear();
let ((xmin, xmax), (ymin, ymax)) = find_dimensions(field);
@@ -53,14 +54,12 @@ fn advance(translation: &Translation, field: &Field, infinity: bool) -> (bool, F
let ny = y + dy;
if nx < xmin || nx > xmax || ny < ymin || ny > ymax {
index |= infinity as usize;
} else {
if field.contains(&(x + dx, y + dy)) {
index |= *infinity as usize;
} else if field.contains(&(x + dx, y + dy)) {
index |= 1;
}
}
}
}
if translation[index] {
new_field.insert((x, y));
@@ -68,17 +67,17 @@ fn advance(translation: &Translation, field: &Field, infinity: bool) -> (bool, F
}
}
(translation[infinity.then(|| 511).unwrap_or(0)], new_field)
*infinity = translation[if *infinity { 511 } else { 0 }]
}
fn parts_common(input: &mut dyn Read, count: usize) -> String {
let (translation, mut field) = read_input(input);
let mut new_field = Field::new();
let mut infinity = false;
for _ in 0..count {
let (new_inf, new_field) = advance(&translation, &field, infinity);
field = new_field;
infinity = new_inf;
advance(&translation, &field, &mut new_field, &mut infinity);
swap(&mut field, &mut new_field);
}
field.len().to_string()