johannes/advent-of-rust-2024
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day 6 part 2 perf

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Johannes
2024-12-06 07:32:13 +01:00
parent 9c5d12c6b0
commit 476f34e2b4
1 changed files with 5 additions and 4 deletions
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9
src/day06.rs
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@@ -82,7 +82,7 @@ fn parse(input: &str) -> (HashMap<Point, char>, Point) {
fn is_loop(m: &HashMap<Point, char>, block: Point, mut pos: Point, mut dir: char) -> bool { fn is_loop(m: &HashMap<Point, char>, block: Point, mut pos: Point, mut dir: char) -> bool {
let mut visited = HashSet::new(); let mut visited = HashSet::new();
while m.contains_key(&pos) { loop {
let (x, y) = pos; let (x, y) = pos;
let next = match dir { let next = match dir {
@@ -92,8 +92,10 @@ fn is_loop(m: &HashMap<Point, char>, block: Point, mut pos: Point, mut dir: char
'>' => (x + 1, y), '>' => (x + 1, y),
_ => unreachable!(), _ => unreachable!(),
}; };
let blocked = next == block || Some(&'#') == m.get(&next); let next_tile = m.get(&next);
if blocked { if None == next_tile {
return false;
} else if next == block || Some(&'#') == next_tile {
// we only check for loops on a collision to speed things up // we only check for loops on a collision to speed things up
if visited.contains(&(pos, dir)) { if visited.contains(&(pos, dir)) {
return true; return true;
@@ -111,7 +113,6 @@ fn is_loop(m: &HashMap<Point, char>, block: Point, mut pos: Point, mut dir: char
pos = next; pos = next;
} }
} }
false
} }
#[cfg(test)] #[cfg(test)]