2024.8

2 files changed, 188 insertions, 0 deletions

diff --git a/2024_rust/inputs/8 b/2024_rust/inputs/8
new file mode 100644
index 0000000..6d6f666
--- /dev/null
+++ b/2024_rust/inputs/8
@@ -0,0 +1,50 @@
+..........1.............TE........................
+....................................R.............
+..................................................
+.......................j.....Q....................
+...................A................8.............
+...........................s.......9...........k..
+q.E..............6...............1R.w.........k...
+..6...E..............1.........R...............t..
+.....r.Q......6........Re..T..............9.......
+.............................T........9...........
+...............................................wv.
+.P............A..................8.v....s.k.......
+.q..................A......k.........8............
+..........o.....1.....W..H............8.......w...
+..Q........P.........O.........e...N.W............
+P................z.........o.............N.......w
+..............o.....p..........Z.s..........N.....
+.....O.x......K.....................v..aN.........
+..O...............U.....H.......t.................
+.E.......q...6.....i..............................
+..............z..........o...i...........aW.......
+....O........r.............e.....Wt...............
+...............U.7i........H......h........t......
+......Q.......n..2...I...A....i.p.................
+...........2...9n.................s........j......
+..q................Ur..........p..................
+.............n.................K..................
+.....S....z.........I.....H.............e.j.......
+..................7..prD..K...d...................
+S.........V.....7....K............................
+......................................0...........
+..................................................
+..................2..........I....j.Z.............
+....................X.............J..Z....a.......
+........SX............................x......0J...
+................U....n........x...............0...
+.........S......X................x....a...........
+...5.......X.......................02.............
+...............V.........................d...J....
+.............................u.......4............
+.....5...........................u.4..............
+....5.............................................
+......V................................3..........
+......D..........................................d
+....D.................................4...........
+.....h....................................d7......
+..............................P...................
+.........D......h........3................u...4...
+.............h..5.....3...........u.....I.........
+..........3......V.............................J..
diff --git a/2024_rust/src/bin/day8.rs b/2024_rust/src/bin/day8.rs
new file mode 100644
index 0000000..cbdfb77
--- /dev/null
+++ b/2024_rust/src/bin/day8.rs
@@ -0,0 +1,138 @@
+use aoc2024::matrix;
+use itertools::Itertools;
+use std::collections::{HashMap, HashSet};
+use std::fmt;
+
+type Freq = char;
+
+enum Dot {
+    Empty,
+    Antenna(Freq),
+}
+use Dot::*;
+
+impl fmt::Display for Dot {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let ch = match self {
+            Empty => &'.',
+            Antenna(c) => c,
+        };
+        write!(f, "{}", ch)
+    }
+}
+
+impl Dot {
+    fn parse(c: char) -> Dot {
+        match c {
+            '.' => Empty,
+            c => Antenna(c),
+        }
+    }
+}
+
+struct M {
+    matrix: matrix::Matrix<Dot>,
+    antennas: HashMap<Freq, HashSet<matrix::Pos>>,
+    antinodes: HashSet<matrix::Pos>,
+}
+
+impl M {
+    fn new(text: &str) -> Self {
+        let matrix = matrix::Matrix::new(text, Dot::parse);
+        let mut antennas: HashMap<Freq, HashSet<matrix::Pos>> = HashMap::new();
+        for i in 0..matrix.limit.0 {
+            for j in 0..matrix.limit.1 {
+                match matrix.get((i, j)) {
+                    Empty => (),
+                    Antenna(freq) => {
+                        antennas.entry(*freq).or_default().insert((i, j));
+                    }
+                }
+            }
+        }
+        M {
+            matrix,
+            antennas,
+            antinodes: HashSet::new(),
+        }
+    }
+
+    fn compute_antinodes(&mut self, version: u8) {
+        for (_freq, antennas) in self.antennas.iter() {
+            // println!("Freq {freq}: {antennas:?}");
+            for (a1, a2) in antennas
+                .into_iter()
+                .permutations(2)
+                .map(|x| x.into_iter().collect_tuple().unwrap())
+            {
+                match version {
+                    0 => {
+                        let an = antinode(a1, a2, &self.matrix.limit);
+                        // println!("  ({a1:?}, {a2:?}) -> {an:?}");
+                        if let Some((x, y)) = an {
+                            self.antinodes.insert((x, y));
+                        }
+                    }
+                    1 => {
+                        for an in antinodes(a1, a2, &self.matrix.limit) {
+                            self.antinodes.insert(an);
+                        }
+                    }
+                    _ => panic!(),
+                }
+            }
+        }
+        // println!("  {:?}", self.antinodes);
+    }
+}
+
+fn antinodes(a1: &matrix::Pos, a2: &matrix::Pos, limit: &matrix::Pos) -> Vec<matrix::Pos> {
+    let mut result = vec![*a1, *a2];
+    let mut a: matrix::Pos = result[0];
+    let mut b: matrix::Pos = result[1];
+    while let Some(an) = antinode(&a, &b, limit) {
+        result.push(an.clone());
+        a = result[result.len() - 2];
+        b = result[result.len() - 1];
+    }
+    result
+}
+
+fn antinode(a1: &matrix::Pos, a2: &matrix::Pos, limit: &matrix::Pos) -> Option<matrix::Pos> {
+    let (x1, y1) = (a1.0 as isize, a1.1 as isize);
+    let (x2, y2) = (a2.0 as isize, a2.1 as isize);
+    let x = x2 - (x1 - x2);
+    let y = y2 - (y1 - y2);
+    if y >= 0 && x >= 0 && y < limit.1 as isize && x < limit.0 as isize {
+        Some((x as usize, y as usize))
+    } else {
+        None
+    }
+}
+
+impl fmt::Display for M {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // write!(f, "{}[2J", 27 as char)?;
+        write!(f, "{}", self.matrix.to_string())
+    }
+}
+
+fn p1(input: &str) -> String {
+    let mut m: M = M::new(input);
+    m.compute_antinodes(0);
+
+    let result = m.antinodes.len();
+    result.to_string()
+}
+
+fn p2(input: &str) -> String {
+    let mut m: M = M::new(input);
+    m.compute_antinodes(1);
+
+    let result = m.antinodes.len();
+    result.to_string()
+}
+
+fn main() {
+    aoc2024::run_day("8", p1, p2);
+}