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|
use regex::Regex;
static DAY: u8 = 15;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", positions_without_beacon(&input, 2000000));
println!("{DAY}b: {}", tuning_frequency(&input, 0, 4000000));
}
#[derive(PartialEq, Eq)]
struct Position {
x: isize,
y: isize,
}
impl Position {
fn distance(&self, other: &Self) -> isize {
(self.x.abs_diff(other.x) + self.y.abs_diff(other.y)) as isize
}
}
struct SensorReading {
sensor: Position,
closest: Position,
range: isize,
}
impl SensorReading {
fn new(input: &str) -> SensorReading {
let re = Regex::new("Sensor at x=(-?[0-9]+), y=(-?[0-9]+): closest beacon is at x=(-?[0-9]+), y=(-?[0-9]+)").unwrap();
let cap = re.captures(input).expect("input should match regex");
let sensor = Position {
x: cap[1].parse::<isize>().unwrap(),
y: cap[2].parse::<isize>().unwrap(),
};
let closest = Position {
x: cap[3].parse::<isize>().unwrap(),
y: cap[4].parse::<isize>().unwrap(),
};
let range = sensor.distance(&closest);
SensorReading { sensor, closest, range }
}
fn signal_in_range(&self, pos: &Position) -> bool {
self.sensor.distance(pos) <= self.range
}
}
fn positions_without_beacon(input: &[String], y: isize) -> usize {
let readings = input.iter()
.map(|x| SensorReading::new(x))
.collect::<Vec<_>>();
let min_x = readings.iter()
.map(|r| r.sensor.x - r.range)
.min().unwrap();
let max_x = readings.iter()
.map(|r| r.sensor.x + r.range)
.max().unwrap();
let mut possible_positions = 0;
for x in min_x ..= max_x {
let pos = Position { x, y };
let in_range = readings.iter()
.any(|r| r.signal_in_range(&pos));
let is_beacon = readings.iter()
.any(|r| r.closest == pos);
if in_range && !is_beacon {
possible_positions += 1;
}
}
possible_positions
}
fn tuning_frequency(input: &[String], min_coord: isize, max_coord: isize) -> isize {
let readings = input.iter()
.map(|x| SensorReading::new(x))
.collect::<Vec<_>>();
let mut x = min_coord;
let mut y = min_coord;
loop {
if x > max_coord {
x = min_coord;
y += 1;
}
let pos = Position { x, y };
let reading = readings.iter()
.find(|r| r.signal_in_range(&pos));
let reading = match reading {
Some(r) => r,
None => return x * 4000000 + y,
};
let dist_y = reading.sensor.y.abs_diff(pos.y) as isize;
/* move position outside of range of current sensor */
x = reading.sensor.x + reading.range + 1 - dist_y;
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"Sensor at x=2, y=18: closest beacon is at x=-2, y=15",
"Sensor at x=9, y=16: closest beacon is at x=10, y=16",
"Sensor at x=13, y=2: closest beacon is at x=15, y=3",
"Sensor at x=12, y=14: closest beacon is at x=10, y=16",
"Sensor at x=10, y=20: closest beacon is at x=10, y=16",
"Sensor at x=14, y=17: closest beacon is at x=10, y=16",
"Sensor at x=8, y=7: closest beacon is at x=2, y=10",
"Sensor at x=2, y=0: closest beacon is at x=2, y=10",
"Sensor at x=0, y=11: closest beacon is at x=2, y=10",
"Sensor at x=20, y=14: closest beacon is at x=25, y=17",
"Sensor at x=17, y=20: closest beacon is at x=21, y=22",
"Sensor at x=16, y=7: closest beacon is at x=15, y=3",
"Sensor at x=14, y=3: closest beacon is at x=15, y=3",
"Sensor at x=20, y=1: closest beacon is at x=15, y=3",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(positions_without_beacon(&input, 10), 26);
assert_eq!(tuning_frequency(&input, 0, 20), 56000011);
}
}
|
