24-11-rs both

1 files changed, 43 insertions, 0 deletions

diff --git a/2024/11/rust/src/main.rs b/2024/11/rust/src/main.rs
new file mode 100644
index 0000000..e352ec4
--- /dev/null
+++ b/2024/11/rust/src/main.rs
@@ -0,0 +1,43 @@
+use std::{collections::HashMap, io};
+
+fn blink(k @ (s, n): (u64, u64), cache: &mut HashMap<(u64, u64), u64>) -> u64 {
+    if n == 0 {
+        return 1;
+    }
+    if let Some(v) = cache.get(&k) {
+        return *v;
+    }
+
+    // cache this
+    let v = {
+        if s == 0 {
+            return blink((1, n - 1), cache);
+        }
+        let digits = s.ilog10() + 1;
+        let mid = 10u64.pow(digits / 2);
+        if digits % 2 == 0 {
+            blink((s / mid, n - 1), cache) + blink((s % mid, n - 1), cache)
+        } else {
+            blink((s * 2024, n - 1), cache)
+        }
+    };
+
+    *cache.entry(k).or_insert(v)
+}
+
+fn main() -> io::Result<()> {
+    let line = io::stdin().lines().flatten().next().unwrap();
+    let stones = line
+        .split_whitespace()
+        .map(|s| s.parse::<u64>().unwrap())
+        .collect::<Vec<_>>();
+
+    let mut cache = HashMap::new();
+    let silver: u64 = stones.iter().map(|s| blink((*s, 25), &mut cache)).sum();
+    let gold: u64 = stones.iter().map(|s| blink((*s, 75), &mut cache)).sum();
+
+    println!("silver: {silver}");
+    println!("gold: {gold}");
+
+    return Ok(());
+}