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[rs] Solve 2022_15 part 2

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This commit is contained in:
Joscha 2022-12-15 10:16:25 +01:00
parent a8291375ba
commit f55cfaccce
2 changed files with 60 additions and 22 deletions
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80
rs/src/y2022/d15.rs
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@ -11,10 +11,44 @@ fn parse_coord(coord: &str) -> i32 {
coord.parse().unwrap()
}
fn line_ranges(sensors: &[Sensor], y: i32) -> Vec<(i32, i32)> {
let mut raw_ranges = vec![];
for sensor in sensors {
let dy = (y - sensor.pos.1).abs();
if dy > sensor.dist {
continue;
}
let dx = sensor.dist - dy;
raw_ranges.push((sensor.pos.0 - dx, sensor.pos.0 + dx));
}
raw_ranges.sort();
let mut ranges = vec![];
let mut raw_ranges = raw_ranges.into_iter();
if let Some(mut cur) = raw_ranges.next() {
for range in raw_ranges {
if cur.0 <= range.0 && range.0 <= cur.1 {
cur.1 = cur.1.max(range.1);
} else {
ranges.push(cur);
cur = range;
}
}
ranges.push(cur);
}
ranges
}
pub fn solve(input: String) {
let sensors = input
.lines()
.map(|l| {
// A beacon exactly dist away has 1 field, i. e. x±0
// A beacon exactly dist-1 away has 3 fields, i. e. x±1
// ...
// A beacon exactly 0 away has 2dist+1 fields, i. e. x±dist
//
// Formula: Go from x-(dist-dy) to x+(dist-dy)
let parts = l.split_whitespace().collect::<Vec<_>>();
let pos = (parse_coord(parts[2]), parse_coord(parts[3]));
let beac = (parse_coord(parts[8]), parse_coord(parts[9]));
@ -23,30 +57,34 @@ pub fn solve(input: String) {
})
.collect::<Vec<_>>();
// A beacon exactly dist away has 1 field, i. e. x±0
// A beacon exactly dist-1 away has 3 fields, i. e. x±1
// ...
// A beacon exactly 0 away has 2dist+1 fields, i. e. x±dist
//
// Formula: Go from x-(dist-dy) to x+(dist-dy)
let line_at_y = 2000000;
let mut part1 = HashSet::new();
for (i, sensor) in sensors.iter().enumerate() {
eprintln!("Sensor {}", i + 1);
let dy = (line_at_y - sensor.pos.1).abs();
if dy > sensor.dist {
continue;
let part1_ranges = line_ranges(&sensors, line_at_y);
let part1_beacons = sensors
.iter()
.filter(|s| s.beac.1 == line_at_y)
.map(|s| s.beac.0)
.collect::<HashSet<_>>();
let mut part1 = 0;
for range in part1_ranges {
part1 += range.1 - range.0 + 1;
for beacon in &part1_beacons {
if range.0 <= *beacon && *beacon <= range.1 {
part1 -= 1;
}
}
}
println!("Part 1: {part1}");
let dx = sensor.dist - dy;
for x in (sensor.pos.0 - dx)..=(sensor.pos.0 + dx) {
part1.insert(x);
for y in 0..=4000000 {
let mut ranges = line_ranges(&sensors, y);
ranges.retain(|(s, e)| *s <= 4000000 && 0 <= *e);
if ranges.len() != 1 {
// Found our beacon!
assert_eq!(ranges.len(), 2);
let x = ranges[0].1 + 1;
let tuning_frequency = x as i64 * 4000000 + y as i64;
println!("Part 2: {tuning_frequency}");
break;
}
}
for sensor in &sensors {
if sensor.beac.1 == line_at_y {
part1.remove(&sensor.beac.0);
}
}
println!("Part 1: {}", part1.len());
}