Advent of Code 2024

[+] Day 8: Resonant Collinearity

adventofcode/Cargo.toml

@@ -13,6 +13,8 @@ bin = [
   { name = "2024-06-02", path = "year2024/day06/part02.rs" },
   { name = "2024-07-01", path = "year2024/day07/part01.rs" },
   { name = "2024-07-02", path = "year2024/day07/part02.rs" },
+  { name = "2024-08-01", path = "year2024/day08/part01.rs" },
+  { name = "2024-08-02", path = "year2024/day08/part02.rs" },
 ]
 
 [package]

adventofcode/year2024/day08/example.txt

@@ -0,0 +1,12 @@
+............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............

adventofcode/year2024/day08/input.txt

@@ -0,0 +1,50 @@
+..............U.............c.....3...............
+.....p.........F..................................
+.....m..7....................4x............3......
+..e.............F..........c...YH..3..............
+.......e...................................c..E..8
+................a...U................8............
+..............................4.F...8....x........
+............7.....4............Hc..E.......x......
+........p..............................E..........
+.............U.e....................x....t........
+.7..........................Z.H....g..............
+.........7..m.....S.........................E.....
+...F.....p...........6...SY.......................
+.................6..k...................g.........
+..........m......a........................g.......
+.......M.......................................g..
+..............a............Y....C........H........
+....u.......6........a.........C.GY...............
+.....M..................S......................2..
+..........M........S.....................2........
+........M.......................5.........z..f....
+.....................................Z........t.2.
+..........6.......................................
+......................................G...........
+.........................A.........G9....Z........
+........................C.........................
+.....k......................G......z..t...........
+.......k......................zs....f........5...9
+................h........................9....2...
+.............h.....0...........f.....K..ZX........
+..................................f...............
+.......1....................9.........Xz..........
+...............1......B.s......X..................
+............h...............B.....................
+..T.........k..................b..................
+...............u..................................
+.........u.............h..................0.......
+..............y...................................
+...............................t....X......5......
+.................A............................5...
+................u..................s..............
+.T..........b....y................................
+............y............................K........
+..1...............................s....B..........
+..............Ay.............B...P................
+..........T.......................K...........0...
+.............T..................P.........K.......
+......A....P......................................
+....b.........1...................................
+.........b................................P.......

adventofcode/year2024/day08/part01.rs

@@ -0,0 +1,78 @@
+use std::{
+    cmp::{max, min},
+    collections::{HashMap, HashSet},
+};
+
+#[derive(Debug)]
+pub struct Map {
+    width: usize,
+    height: usize,
+    antennas: HashMap<char, HashSet<(usize, usize)>>,
+}
+
+impl Map {
+    pub fn parse(text: &str) -> Self {
+        let (mut width, mut height) = (0, 0);
+        let mut antennas = HashMap::new();
+
+        text.split("\n")
+            .filter(|l| !l.is_empty())
+            .enumerate()
+            .for_each(|(y, cs)| {
+                height = max(y, height);
+                cs.char_indices().for_each(|(x, c)| {
+                    width = max(x, width);
+                    if c != '.' {
+                        antennas.entry(c).or_insert(HashSet::new()).insert((x, y));
+                    }
+                })
+            });
+
+        Map {
+            width,
+            height,
+            antennas,
+        }
+    }
+
+    pub fn antinodes(&self) -> HashSet<(usize, usize)> {
+        let mut antinodes = HashSet::new();
+        let (width, height) = (self.width as isize, self.height as isize);
+
+        self.antennas.values().for_each(|points| {
+            for (i, (px, py)) in points.iter().enumerate() {
+                let (px, py) = (*px, *py);
+                for (qx, qy) in points.iter().skip(i + 1) {
+                    let (qx, qy) = (*qx, *qy);
+                    let dx = px as isize - qx as isize;
+                    let dy = py as isize - qy as isize;
+
+                    let ax = qx as isize - dx;
+                    let ay = qy as isize - dy;
+
+                    if ax >= 0 && ax <= width && ay >= 0 && ay <= height {
+                        antinodes.insert((ax as usize, ay as usize));
+                    }
+
+                    let bx = px as isize + dx;
+                    let by = py as isize + dy;
+
+                    if bx >= 0 && bx <= width && by >= 0 && by <= height {
+                        antinodes.insert((bx as usize, by as usize));
+                    }
+                }
+            }
+        });
+
+        antinodes
+    }
+}
+
+fn main() {
+    let text = std::fs::read_to_string("input.txt").unwrap();
+    let map = Map::parse(&text);
+    let antinodes = map.antinodes();
+
+    let answer = antinodes.len();
+    println!("{}", answer);
+}

adventofcode/year2024/day08/part02.rs

@@ -0,0 +1,83 @@
+use std::{
+    cmp::max,
+    collections::{HashMap, HashSet},
+};
+
+#[derive(Debug)]
+pub struct Map {
+    width: usize,
+    height: usize,
+    antennas: HashMap<char, HashSet<(usize, usize)>>,
+}
+
+impl Map {
+    pub fn parse(text: &str) -> Self {
+        let (mut width, mut height) = (0, 0);
+        let mut antennas = HashMap::new();
+
+        text.split("\n")
+            .filter(|l| !l.is_empty())
+            .enumerate()
+            .for_each(|(y, cs)| {
+                height = max(y, height);
+                cs.char_indices().for_each(|(x, c)| {
+                    width = max(x, width);
+                    if c != '.' {
+                        antennas.entry(c).or_insert(HashSet::new()).insert((x, y));
+                    }
+                })
+            });
+
+        Map {
+            width,
+            height,
+            antennas,
+        }
+    }
+
+    pub fn antinodes(&self) -> HashSet<(usize, usize)> {
+        let mut antinodes = HashSet::new();
+        let (width, height) = (self.width as isize, self.height as isize);
+
+        self.antennas.values().for_each(|points| {
+            for (px, py) in points.iter() {
+                let (px, py) = (*px, *py);
+
+                for (qx, qy) in points.iter() {
+                    let (qx, qy) = (*qx, *qy);
+
+                    if px == qx && py == qy {
+                        continue;
+                    }
+
+                    let dx = px as isize - qx as isize;
+                    let dy = py as isize - qy as isize;
+
+                    let k = max(width / dx, height / dy);
+
+                    let mut x = qx as isize - k * dx;
+                    let mut y = qy as isize - k * dy;
+
+                    for _ in 1..(2 * k) {
+                        x += dx;
+                        y += dy;
+                        if x >= 0 && x <= width && y >= 0 && y <= height {
+                            antinodes.insert((x as usize, y as usize));
+                        }
+                    }
+                }
+            }
+        });
+
+        antinodes
+    }
+}
+
+fn main() {
+    let text = std::fs::read_to_string("input.txt").unwrap();
+    let map = Map::parse(&text);
+    let antinodes = map.antinodes();
+
+    let answer = antinodes.len();
+    println!("{}", answer);
+}