solution: day 19

src/days.rs

@@ -16,7 +16,7 @@ pub mod d15;
 pub mod d16;
 pub mod d17;
 pub mod d18;
-// pub mod d19;
+pub mod d19;
 // pub mod d20;
 // pub mod d21;
 // pub mod d22;

src/days/d19.rs

@@ -0,0 +1,42 @@
+use crate::prelude::*;
+
+pub type I = u32;
+pub type O = u32;
+
+fn _silver (data: I) -> O {
+    2 * (data - (1 << (32 - data.leading_zeros() - 1))) + 1
+}
+
+fn _gold (data: I) -> O {
+    let mut left = D::from_iter(0..data/2);
+    let mut right = D::from_iter(data/2..data);
+
+    while !left.is_empty() && !right.is_empty() {
+        if left.len() > right.len() {
+            left.pop_back();
+        } else {
+            right.pop_back();
+        }
+        right.push_front(left.pop_front().unwrap());
+        left.push_back(right.pop_back().unwrap());
+    }
+
+    left[0] + 1
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn silver () {
+        let ans = _silver(3005290);
+        assert_eq!(ans, 1816277)
+    }
+
+    #[test]
+    fn gold () {
+        let ans = _gold(3005290);
+        assert_eq!(ans, 1)
+    }
+}