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day6: performance - only check obstacles on the original path

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700ms -> 150ms
This commit is contained in:
Keenan Tims
2024-12-06 10:59:43 -08:00
parent 1cd535c2aa
commit b1918bbebf
1 changed files with 16 additions and 12 deletions
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28
6/src/main.rs
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@@ -216,21 +216,25 @@ fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
// PROBLEM 2 solution
fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
let input_map = Map::from(input);
// Use the solution from problem 1 to reduce the number of positions where obstacle placement will change the path
let mut part1 = input_map.clone();
part1.run_guard();
let mut loop_count = 0u64;
for y in 0..input_map.grid.height() {
for x in 0..input_map.grid.width() {
match input_map.grid.get(x as i64, y as i64) {
Some(b'.') => {
let mut test_map = input_map.clone();
test_map.grid.set(x as i64, y as i64, b'#');
if let RunOutcome::LoopFound = test_map.run_guard() {
loop_count += 1
}
}
_ => continue,
}
for pos in part1
.grid
.data
.iter()
.enumerate()
.filter_map(|(pos, c)| if *c == b'X' { Some(pos) } else { None })
{
let mut test_map = input_map.clone();
test_map.grid.data[pos] = b'#';
if let RunOutcome::LoopFound = test_map.run_guard() {
loop_count += 1
}
}
loop_count
}