add: combined solution to d01

2025/01/all.rs

@@ -0,0 +1,34 @@
+type SmolI = i32;
+
+#[unsafe(no_mangle)]
+unsafe extern "Rust" fn challenge_isize_duple(buf: &[u8]) -> (isize, isize) {
+    let mut count_p1 = 0;
+    let mut count_p2 = 0;
+    let mut pos = 50;
+
+    let buf = unsafe { str::from_utf8_unchecked(buf.get_unchecked(..(buf.len() - 1))) };
+
+    for ln in buf.split('\n') {
+        let (dir, amt) = unsafe { (*ln.as_bytes().get_unchecked(0), ln.get_unchecked(1..)) };
+
+        let amt: SmolI = unsafe { amt.parse().unwrap_unchecked() };
+        if amt == 0 { continue; }
+        let prev_pos = pos;
+        pos += ((((dir == b'R') as SmolI) << 1) - 1) * amt;
+
+        count_p2 += if pos < 0 {
+            if prev_pos == 0 {
+                count_p2 -= 1;
+            };
+            (pos - 1).div_euclid(100).abs()
+        } else if pos > 0 {
+            pos.div_euclid(100)
+        } else {
+            1
+        };
+        pos = pos.rem_euclid(100);
+        count_p1 += (pos == 0) as SmolI;
+    }
+
+    (count_p1 as isize, count_p2 as isize)
+}