AOC 2024 day 08

Signed-off-by: Mårten Kongstad <[email protected]>

2024/08/Cargo.toml

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+[package]
+name = "aoc-2024-08"
+version = "0.1.0"
+authors = ["Mårten Kongstad <[email protected]>"]
+edition = "2021"
+
+[dependencies]
+anyhow = "1.0"
+aoc = { path = "../../aoc" }

2024/08/src/input.txt

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+...........6.b....................................
+........6................8........................
+..Y.......................................o.......
+....V...j............B.............c..............
+............8.........X.......L...................
+.....j..v6.......3.L..................c...........
+..Mj.....p3.......b........Z....................J.
+..........M...X...................................
+V..............v......p.........Z.........c.......
+..............3...................................
+.......V......U3.............c....................
+..........b..v.M.U8...............................
+..........j........8.....................J........
+..........Y......q........LH..Z...D...........y...
+..2Y........PX......6..................BQ.........
+...0.Y...............XP...........w...............
+.........U.......2...............oH.y.............
+0..............9........U.........................
+...........P..............W.......z...Oy..........
+...................t...p.W..o.............Q.......
+.....S.................t.....Q....B...............
+S.k..................V..W...p.......H...O......m..
+....S.h................W.......................O..
+..h..P.2.............Z.............J..............
+.........k.......5v.......q...t.s.................
+.....Q.....h..........................J...B.......
+........0.........l...............................
+.S................................................
+.............................M....................
+2..................e.....o.....y..................
+................k.................................
+......4......k....t...s.q.........................
+.4.......................q........................
+.......................z....E.....................
+.............0.....d..............................
+7..........D........z.............................
+.......D..5......7..9.............................
+......5..................E........................
+D..............K......d..9E..........w.....1..C...
+.......K..x.........d....s...........l............
+........7......................u...C..............
+..K........x..............9..C...u................
+4..............s.........................l...T..w.
+.......5.....7..................m......T......1...
+...........................E...z.m................
+......................................u...C.......
+.............................em...................
+..............................................T...
+....................x.......................e.....
+.............................1e....w....l.........

2024/08/src/main.rs

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+use anyhow::{bail, Result};
+use aoc::{BoundingBox, XY};
+use std::collections::{HashMap, HashSet};
+
+fn main() -> Result<()> {
+    let input = include_str!("input.txt");
+    aoc::run!(part_one(input), 305)?;
+    aoc::run!(part_two(input), 1150)?;
+    Ok(())
+}
+
+type AntennaMap = HashMap<char, Vec<XY>>;
+
+fn parse(input: &str) -> Result<(AntennaMap, BoundingBox)> {
+    let mut antennas: AntennaMap = HashMap::new();
+    let bounding_box = aoc::parse_grid(input, |xy, ch| match ch {
+        '.' => Ok(()),
+        ch if ch.is_ascii_alphanumeric() => {
+            antennas.entry(ch).or_default().push(xy);
+            Ok(())
+        }
+        _ => bail!("unexpected char {ch}"),
+    })?;
+    Ok((antennas, bounding_box))
+}
+
+fn part_x(input: &str, part_two_specifics: bool) -> Result<usize> {
+    let (antennas, bb) = parse(input)?;
+    let mut signals: HashSet<XY> = HashSet::new();
+    for v in antennas.values() {
+        for a in v {
+            if part_two_specifics {
+                signals.insert(*a);
+            }
+            for b in v {
+                if a == b {
+                    continue;
+                }
+                let step = a - b;
+                let mut xy = *a;
+                loop {
+                    xy += step;
+                    if bb.contains(&xy) {
+                        signals.insert(xy);
+                    } else {
+                        break;
+                    }
+                    if !part_two_specifics {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+    Ok(signals.len())
+}
+
+fn part_one(input: &str) -> Result<usize> {
+    part_x(input, false)
+}
+
+fn part_two(input: &str) -> Result<usize> {
+    part_x(input, true)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = include_str!("test-input.txt");
+
+    #[test]
+    fn test_part_one() {
+        assert_eq!(part_one(INPUT).unwrap(), 14);
+    }
+
+    #[test]
+    fn test_part_two() {
+        assert_eq!(part_two(INPUT).unwrap(), 34);
+    }
+}

2024/08/src/test-input.txt

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+............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............