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#![allow(dead_code)]
#![allow(unused_variables)]
use advent_of_code::prelude::*;
fn dist(a: (IRow, ICol), b: (IRow, ICol)) -> usize {
a.0.abs_diff(b.0).0 + a.1.abs_diff(b.1).0
}
#[derive(Debug, Copy, Clone)]
struct Sensor {
pos: (IRow, ICol),
beacon: (IRow, ICol),
radius: usize,
}
impl Sensor {
fn new(pos: (IRow, ICol), beacon: (IRow, ICol)) -> Self {
Self {
pos,
beacon,
radius: dist(pos, beacon),
}
}
fn row_radius(&self, row: IRow) -> usize {
self.radius - self.pos.0.abs_diff(row).0
}
fn in_radius(&self, pos: (IRow, ICol)) -> bool {
dist(self.pos, pos) <= self.radius
}
}
pub struct Map {
sensors: Vec<Sensor>,
}
impl Map {
fn new(mut sensors: Vec<Sensor>) -> Self {
sensors.sort_unstable_by(|a, b| b.radius.cmp(&a.radius));
Self { sensors }
}
fn nearby_sensor(&self, pos: (IRow, ICol)) -> Option<Sensor> {
self.sensors
.iter()
.copied()
.find(|sensor| sensor.in_radius(pos))
}
fn beacons(&self) -> HashSet<(IRow, ICol)> {
self.sensors
.iter()
.copied()
.map(|sensor| sensor.beacon)
.collect()
}
}
pub fn parse(fh: File) -> Result<Map> {
let mut sensors = vec![];
for line in parse::raw_lines(fh) {
let cap = regex_captures!(r"Sensor at x=(-?\d+), y=(-?\d+): closest beacon is at x=(-?\d+), y=(-?\d+)", &line)
.ok_or_else(|| anyhow::anyhow!("no match"))?;
let sensor_x: isize = cap[1].parse()?;
let sensor_y: isize = cap[2].parse()?;
let beacon_x: isize = cap[3].parse()?;
let beacon_y: isize = cap[4].parse()?;
sensors.push(Sensor::new(
(IRow(sensor_y), ICol(sensor_x)),
(IRow(beacon_y), ICol(beacon_x)),
));
}
Ok(Map::new(sensors))
}
pub fn part1(mut map: Map) -> Result<usize> {
let row = IRow(2_000_000);
map.sensors = map
.sensors
.iter()
.copied()
.filter(|sensor| {
((sensor.pos.0 - sensor.radius as isize)
..=(sensor.pos.0 + sensor.radius as isize))
.contains(&row)
})
.collect();
let min_sensor = map
.sensors
.iter()
.min_by_key(|sensor| sensor.pos.1)
.unwrap();
let max_sensor = map
.sensors
.iter()
.max_by_key(|sensor| sensor.pos.1)
.unwrap();
let mut total = 0;
let mut col = min_sensor.pos.1 - min_sensor.row_radius(row) as isize;
while col < max_sensor.pos.1 + max_sensor.row_radius(row) as isize {
if let Some(sensor) = map.nearby_sensor((row, col)) {
let row_radius = sensor.radius - sensor.pos.0.abs_diff(row).0;
let skip = (sensor.pos.1 - col.0).0 as usize + row_radius + 1;
total += skip;
col = col + skip as isize;
} else {
col = col + 1;
}
}
Ok(total
- map
.beacons()
.iter()
.filter(|beacon| beacon.0 == row)
.count())
}
pub fn part2(map: Map) -> Result<isize> {
for row in (0..=4_000_000).map(IRow) {
let mut col = ICol(0);
while col <= ICol(4_000_000) {
if let Some(sensor) = map.nearby_sensor((row, col)) {
col = sensor.pos.1 + sensor.row_radius(row) as isize + 1;
} else {
return Ok((col.0) * 4_000_000 + (row.0));
}
}
}
panic!("couldn't find beacon");
}
#[test]
fn test() {
assert_eq!(
part1(parse(parse::data(2022, 15).unwrap()).unwrap()).unwrap(),
4737443
);
assert_eq!(
part2(parse(parse::data(2022, 15).unwrap()).unwrap()).unwrap(),
11482462818989
);
}
|
