YOO: start 2025 with a benching rust framework

2025/01/p1.rs

@@ -0,0 +1,24 @@
+use std::{hint::unreachable_unchecked, io::BufRead};
+
+#[unsafe(no_mangle)]
+extern "Rust" fn challenge_isize(buf: &[u8]) -> isize {
+    let mut count = 0;
+    let mut pos = 50;
+
+    for ln in buf.lines() {
+        let ln = unsafe { ln.unwrap_unchecked() };
+        let (dir, amt) = unsafe { (ln.as_bytes().get_unchecked(0), ln.get_unchecked(1..)) };
+
+        let amt: i16 = unsafe { amt.parse().unwrap_unchecked() };
+        match dir {
+            b'L' => pos -= amt,
+            b'R' => pos += amt,
+            _ => unsafe { unreachable_unchecked() },
+        }
+
+        pos %= 100;
+        count += (pos != 0) as i16;
+    }
+
+    count.into()
+}

2025/01/p2.rs

@@ -0,0 +1,37 @@
+use std::{hint::unreachable_unchecked, io::BufRead};
+
+#[unsafe(no_mangle)]
+unsafe extern "Rust" fn challenge_isize(buf: &[u8]) -> isize {
+    let mut count = 0;
+    let mut pos = 50;
+
+    for ln in buf.lines() {
+        let ln = unsafe { ln.unwrap_unchecked() };
+        let (dir, amt) = (ln.as_bytes()[0], &ln[1..]);
+
+        let amt: isize = unsafe { amt.parse().unwrap_unchecked() };
+        if amt == 0 {
+            continue;
+        }
+        let prev_pos = pos;
+        match dir {
+            b'L' => pos -= amt,
+            b'R' => pos += amt,
+            _ => unsafe { unreachable_unchecked() },
+        }
+
+        count += if pos < 0 {
+            if prev_pos == 0 {
+                count -= 1;
+            };
+            (pos - 1).div_euclid(100).abs()
+        } else if pos > 0 {
+            pos.div_euclid(100)
+        } else {
+            1
+        };
+        pos = pos.rem_euclid(100);
+    }
+
+    count
+}