3 files changed, 87 insertions, 0 deletions
diff --git a/2024/08/rust/Cargo.lock b/2024/08/rust/Cargo.lock
new file mode 100644
index 0000000..e91e374
--- /dev/null
+++ b/2024/08/rust/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "aoc_2024-08"
+version = "0.1.0"
diff --git a/2024/08/rust/Cargo.toml b/2024/08/rust/Cargo.toml
new file mode 100644
index 0000000..bb3b056
--- /dev/null
+++ b/2024/08/rust/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "aoc_2024-08"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/2024/08/rust/src/main.rs b/2024/08/rust/src/main.rs
new file mode 100644
index 0000000..4fc3286
--- /dev/null
+++ b/2024/08/rust/src/main.rs
@@ -0,0 +1,74 @@
+use std::{
+    collections::{HashMap, HashSet},
+    io,
+};
+
+fn main() -> io::Result<()> {
+    let mut antennae: HashMap<char, Vec<(i32, i32)>> = HashMap::new();
+
+    let grid = io::stdin()
+        .lines()
+        .flatten()
+        .map(|s| s.chars().collect())
+        .collect::<Vec<Vec<char>>>();
+
+    let max = grid.first().unwrap().len() as i32;
+    let may = grid.len() as i32;
+    grid.iter()
+        .enumerate()
+        .flat_map(|(y, row)| {
+            row.iter()
+                .enumerate()
+                .filter(|(_, &c)| c != '.')
+                .map(move |(x, &c)| (c, (x as i32, y as i32)))
+        })
+        .for_each(|(c, p)| antennae.entry(c).or_default().push(p));
+
+    let mut silver = HashSet::new();
+    let mut gold = HashSet::new();
+    for ps in antennae.values() {
+        for (n, &p) in ps.iter().enumerate() {
+            for &t in &ps[n+1..] {
+                antinodes(p, t, (max, may), false).for_each(|n| {
+                    silver.insert(n);
+                });
+                antinodes(p, t, (max, may), true).for_each(|n| {
+                    gold.insert(n);
+                });
+            }
+        }
+    }
+
+    let silver = silver.len();
+    let gold = gold.len();
+    println!("silver: {silver}");
+    println!("gold: {gold}");
+
+    return Ok(());
+}
+
+fn antinodes(
+    a: (i32, i32),
+    b: (i32, i32),
+    max: (i32, i32),
+    gold: bool,
+) -> impl Iterator<Item = (i32, i32)> {
+    let dx = b.0 - a.0;
+    let dy = b.1 - a.1;
+    let in_range = move |(x, y)| (0..max.0).contains(&x) && (0..max.1).contains(&y);
+    if !gold {
+        vec![(a.0 - dx, a.1 - dy), (b.0 + dx, b.1 + dy)]
+    } else {
+        (0..)
+            .map(|n| (a.0 - n * dx, a.1 - n * dy))
+            .take_while(move |&p| in_range(p))
+            .chain(
+                (0..)
+                    .map(|n| (b.0 + n * dx, b.1 + n * dy))
+                    .take_while(move |&p| in_range(p)),
+            )
+            .collect()
+    }
+    .into_iter()
+    .filter(move |&p| in_range(p))
+}