1 files changed, 84 insertions, 0 deletions
diff --git a/aoc/2025/11/rust/src/main.rs b/aoc/2025/11/rust/src/main.rs
new file mode 100644
index 0000000..522d7ad
--- /dev/null
+++ b/aoc/2025/11/rust/src/main.rs
@@ -0,0 +1,84 @@
+use std::{cell::RefCell, collections::HashMap, io, rc::Rc};
+
+#[derive(PartialEq, Eq, Hash, Debug)]
+struct Node {
+    device: String,
+    dac: bool,
+    fft: bool,
+}
+
+fn main() {
+    let adj = io::stdin()
+        .lines()
+        .flatten()
+        .map(|line| {
+            let (k, v) = line.split_once(": ").unwrap();
+            (
+                String::from(k),
+                String::from(v)
+                    .split_whitespace()
+                    .map(String::from)
+                    .collect(),
+            )
+        })
+        .collect::<HashMap<String, Vec<String>>>();
+
+    let cache = Rc::new(RefCell::new(HashMap::new()));
+
+    let silver = paths_from(
+        Node {
+            device: String::from("you"),
+            dac: true,
+            fft: true,
+        },
+        &adj,
+        Rc::clone(&cache),
+    );
+    let gold = paths_from(
+        Node {
+            device: String::from("svr"),
+            dac: false,
+            fft: false,
+        },
+        &adj,
+        Rc::clone(&cache),
+    );
+
+    println!("silver: {silver}");
+    println!("gold: {gold}");
+}
+
+fn paths_from(
+    curr: Node,
+    adj: &HashMap<String, Vec<String>>,
+    cache: Rc<RefCell<HashMap<Node, usize>>>,
+) -> usize {
+    if curr.device == "out" {
+        if curr.dac && curr.fft {
+            return 1;
+        }
+        return 0;
+    }
+
+    let Some(&v) = cache.borrow().get(&curr) else {
+        let paths = adj
+            .get(&curr.device)
+            .unwrap()
+            .iter()
+            .map(|n| {
+                paths_from(
+                    Node {
+                        device: n.clone(),
+                        dac: curr.dac || curr.device == "dac",
+                        fft: curr.fft || curr.device == "fft",
+                    },
+                    adj,
+                    Rc::clone(&cache),
+                )
+            })
+            .sum();
+        cache.borrow_mut().insert(curr, paths);
+        return paths;
+    };
+    return v;
+}