1 files changed, 100 insertions, 0 deletions
diff --git a/aoc/2024/09/rust/src/main.rs b/aoc/2024/09/rust/src/main.rs
new file mode 100644
index 0000000..fa7c021
--- /dev/null
+++ b/aoc/2024/09/rust/src/main.rs
@@ -0,0 +1,100 @@
+#![feature(iter_array_chunks)]
+
+use std::io;
+
+fn main() -> io::Result<()> {
+    let disk_map = io::stdin()
+        .lines()
+        .flatten()
+        .next()
+        .unwrap()
+        .chars()
+        .map(|c| c as u8 - b'0')
+        .collect();
+
+    let silver: usize = silver(&disk_map);
+    let gold: usize = gold(&disk_map);
+    println!("silver: {silver}");
+    println!("gold: {gold}");
+
+    return Ok(());
+}
+
+fn silver(input: &Vec<u8>) -> usize {
+    let mut blocks = input
+        .iter()
+        .chain([0, 0].iter()) // lol
+        .array_chunks()
+        .enumerate()
+        .map(|(n, [&f, &s])| [[Some(n)].repeat(f as usize), [None].repeat(s as usize)])
+        .flatten()
+        .flatten()
+        .collect::<Vec<_>>();
+
+    let mut l = 0;
+    let mut r = blocks.len() - 1;
+    loop {
+        while blocks[r].is_none() {
+            r -= 1;
+        }
+        while blocks[l].is_some() {
+            l += 1;
+        }
+        if l >= r {
+            break;
+        }
+        let [left, right] = blocks.get_disjoint_mut([l, r]).unwrap();
+        left.replace(right.take().unwrap());
+    }
+
+    blocks
+        .iter()
+        .enumerate()
+        .map(|(n, id)| n * id.unwrap_or_default())
+        .sum()
+}
+
+fn gold(input: &Vec<u8>) -> usize {
+    let mut blocks = input
+        .iter()
+        .chain([0, 0].iter()) // lol
+        .array_chunks()
+        .enumerate()
+        .map(|(n, [&f, &s])| [(Some(n), f as usize), (None, s as usize)])
+        .flatten()
+        .collect::<Vec<_>>();
+
+    let mut r = blocks.len();
+    while r > 0 {
+        r -= 1;
+        let (Some(_), f) = blocks[r] else {
+            continue;
+        };
+
+        // find some empty space and maybe split
+        let Some(l) = blocks.iter().position(|b| b.0.is_none() && b.1 >= f) else {
+            continue;
+        };
+        if l > r {
+            continue;
+        };
+
+        let (_, s) = &mut blocks[l];
+
+        let diff = *s - f;
+        if diff > 0 {
+            *s = f;
+            blocks.insert(l + 1, (None, diff));
+            r += 1;
+        }
+        blocks.swap(l, r);
+    }
+
+    blocks
+        .iter()
+        .map(|&(id, n)| [id].repeat(n))
+        .flatten()
+        .enumerate()
+        .map(|(n, id)| n * id.unwrap_or_default())
+        .sum()
+}