add: d11p1

2025/11/p1.rs

@@ -0,0 +1,37 @@
+#![feature(slice_split_once)]
+
+use std::collections::HashMap;
+
+#[unsafe(no_mangle)]
+pub unsafe extern "Rust" fn challenge_usize(buf: &[u8]) -> usize {
+    let conns = buf[..(buf.len() - 1)]
+        .split(|&b| b == b'\n')
+        .map(|ln| {
+            let (left, right) = ln.split_once(|&b| b == b':').unwrap();
+            let conns = unsafe { str::from_utf8_unchecked(right) }
+                .trim()
+                .split(' ')
+                .collect::<Vec<_>>();
+
+            (unsafe { str::from_utf8_unchecked(left) }, conns)
+        })
+        .collect::<HashMap<_, _>>();
+
+    println!("{conns:#?}");
+
+    count_paths(&conns, "you")
+}
+
+fn count_paths(set: &HashMap<&str, Vec<&str>>, from: &str) -> usize {
+    let mut count = 0;
+
+    for &subk in set.get(from).unwrap() {
+        if subk == "out" {
+            count += 1;
+        } else {
+            count += count_paths(set, subk);
+        }
+    }
+
+    count
+}