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day18: small optimization - avoid duplicates

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not sure if the input contains dupes, but avoid doing a second path
search if the square already contains a byte, seems like a small
performance gain
This commit is contained in:
Keenan Tims 2024-12-18 00:40:44 -08:00
parent 9a6ca66059
commit b588837624
Signed by: ktims
GPG Key ID: 11230674D69038D4
1 changed files with 14 additions and 12 deletions
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14
src/day18.rs
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@ -51,10 +51,12 @@ impl MemoryMap {
Self { map, byte_stream } Self { map, byte_stream }
} }
fn place_byte(&mut self, i: usize) { // Return if the byte caused a new blockage or not
fn place_byte(&mut self, i: usize) -> bool {
let pos = self.byte_stream[i]; let pos = self.byte_stream[i];
if self.map.set(&pos, false).is_none() { match self.map.set(&pos, false) {
panic!("corruption outside memory bounds"); None => panic!("corruption outside memory bounds"),
Some(x) => x,
} }
} }
fn place_bytes(&mut self, n: usize) { fn place_bytes(&mut self, n: usize) {
@ -126,11 +128,10 @@ pub fn part2_impl(input: &str, width: usize, height: usize, n: usize) -> (i64, i
input_map.place_bytes(n); input_map.place_bytes(n);
let mut path = input_map.dijkstra::<Vec<(i64, i64)>>((0, 0)).expect("no path found"); let mut path = input_map.dijkstra::<Vec<(i64, i64)>>((0, 0)).expect("no path found");
println!("{:?}", path);
for byte in n..input_map.byte_stream.len() { for byte in n..input_map.byte_stream.len() {
input_map.place_byte(byte); if input_map.place_byte(byte) {
// If it's a new blockage, and it obstructs our best path, we need to do a new path search
if let Some((obs_at, _)) = path.iter().find_position(|v| *v == &input_map.byte_stream[byte]) { if let Some((obs_at, _)) = path.iter().find_position(|v| *v == &input_map.byte_stream[byte]) {
let (before, _) = path.split_at(obs_at); let (before, _) = path.split_at(obs_at);
@ -141,6 +142,7 @@ pub fn part2_impl(input: &str, width: usize, height: usize, n: usize) -> (i64, i
} }
} }
} }
}
panic!("no bytes block route"); panic!("no bytes block route");
} }