1 files changed, 132 insertions, 21 deletions

diff --git a/day1/src/main.rs b/day1/src/main.rs
index 5931c59..2058021 100644
--- a/day1/src/main.rs
+++ b/day1/src/main.rs
@@ -33,13 +33,64 @@ impl FromStr for Rotation {
     }
 }
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
 struct Dial(u8);
 
+struct RotateResult(u32, Dial);
+
 impl Dial {
     fn new() -> Self {
         Self(50)
     }
+
+    fn rotate(self, rot: &Rotation) -> RotateResult {
+        match rot {
+            Rotation::Left(n) => self.rotate_left(*n),
+            Rotation::Right(n) => self.rotate_right(*n),
+        }
+    }
+
+    fn rotate_left(self, n: u32) -> RotateResult {
+        let pos = self.0 as u32;
+
+        if pos != 0 && n >= pos {
+            let quot = n.div_ceil(100);
+            RotateResult(quot, self - n)
+        } else {
+            RotateResult(0, self - n)
+        }
+    }
+
+    fn rotate_right(self, n: u32) -> RotateResult {
+        let pos = self.0 as u32;
+
+        if n + pos >= 100 {
+            let quot = n.div_ceil(100);
+            RotateResult(quot, self + n)
+        } else {
+            RotateResult(0, self + n)
+        }
+    }
+
+    fn rotate_all(self, rotations: &[Rotation]) -> RotateResult {
+        let mut dial = Dial::from(50);
+        let mut zeros_total = 0;
+
+        for rot in rotations {
+            let RotateResult(zeros, new_dial) = dial.rotate(rot);
+            zeros_total += zeros;
+            dial = new_dial;
+            println!("{:?}, dial: {}, zeros: {}", rot, dial.0, zeros);
+        }
+
+        RotateResult(zeros_total, dial)
+    }
+}
+
+impl From<u8> for Dial {
+    fn from(value: u8) -> Self {
+        Self(value)
+    }
 }
 
 impl Add<u32> for Dial {
@@ -68,28 +119,14 @@ impl PartialEq<u8> for Dial {
     }
 }
 
-fn main() -> anyhow::Result<()> {
-    let mut args = env::args();
-    let input_path = args.nth(1).ok_or(anyhow!("usage: day1 INPUT"))?;
-    let input = fs::read_to_string(input_path)?;
-
-    let rotations: Vec<Rotation> = input
-        .split_whitespace()
-        .map(|s| s.parse().map_err(|_| anyhow!("bad rotation: {}", s)))
-        .collect::<anyhow::Result<_>>()?;
-
-    println!("rotations: {}", rotations.len());
-
+fn part1(rotations: &[Rotation]) -> RotateResult {
     let mut dial = Dial::new();
     let mut zeros = 0;
 
     for rot in rotations {
-        println!("dial: {}", dial.0);
-        println!("rotation: {:?}", rot);
-
         match rot {
-            Rotation::Left(n) => dial = dial - n,
-            Rotation::Right(n) => dial = dial + n,
+            Rotation::Left(n) => dial = dial - *n,
+            Rotation::Right(n) => dial = dial + *n,
         }
 
         if dial == 0 {
@@ -97,9 +134,45 @@ fn main() -> anyhow::Result<()> {
         }
     }
 
-    println!("zeros: {}", zeros);
+    RotateResult(zeros, dial)
+}
+
+fn main() -> anyhow::Result<()> {
+    let usage_err = || anyhow!("usage: day1 PART INPUT");
+
+    let mut args = env::args();
+
+    let part: u8 = args
+        .nth(1)
+        .ok_or_else(usage_err)?
+        .parse()
+        .map_err(|_| usage_err())?;
+
+    let input_path = args.next().ok_or_else(usage_err)?;
+
+    let input = fs::read_to_string(input_path)?;
+
+    let rotations: Vec<Rotation> = input
+        .split_whitespace()
+        .map(|s| s.parse().map_err(|_| anyhow!("bad rotation: {}", s)))
+        .collect::<anyhow::Result<_>>()?;
+
+    match part {
+        1 => {
+            let RotateResult(zeros, _) = part1(&rotations);
+            println!("Result: {}", zeros);
+            Ok(())
+        }
+
+        2 => {
+            let dial = Dial::from(50);
+            let RotateResult(zeros, _) = dial.rotate_all(&rotations);
+            println!("Result: {}", zeros);
+            Ok(())
+        }
 
-    Ok(())
+        _ => Err(usage_err()),
+    }
 }
 
 #[cfg(test)]
@@ -122,7 +195,7 @@ mod tests {
     }
 
     #[test]
-    fn dial() {
+    fn dial_ops() {
         let dial = Dial::new();
 
         assert_eq!(dial + 1, 51);
@@ -143,4 +216,42 @@ mod tests {
         assert_eq!(dial - 51, 99);
         assert_eq!(dial - 50, 0);
     }
+
+    #[test]
+    fn dial_rotate() {
+        let mut dial = Dial::new();
+
+        let rotations = vec![
+            // Example data
+            (Rotation::Left(68), 1, 82),
+            (Rotation::Left(30), 0, 52),
+            (Rotation::Right(48), 1, 0),
+            (Rotation::Left(5), 0, 95),
+            (Rotation::Right(60), 1, 55),
+            (Rotation::Left(55), 1, 0),
+            (Rotation::Left(1), 0, 99),
+            (Rotation::Left(99), 1, 0),
+            (Rotation::Right(14), 0, 14),
+            (Rotation::Left(82), 1, 32),
+            // Additional data
+            (Rotation::Left(200), 2, 32),
+            (Rotation::Right(200), 2, 32),
+            (Rotation::Left(30), 0, 2),
+            (Rotation::Left(10), 1, 92),
+            (Rotation::Right(10), 1, 2),
+            (Rotation::Left(110), 2, 92),
+            (Rotation::Right(210), 3, 2),
+            (Rotation::Right(48), 0, 50),
+            (Rotation::Right(1000), 10, 50),
+            (Rotation::Right(48), 0, 98),
+            (Rotation::Left(651), 6, 47),
+        ];
+
+        for (rot, expected_zeros, expected_dial) in &rotations {
+            let RotateResult(zeros, new_dial) = dial.rotate(rot);
+            assert_eq!(&zeros, expected_zeros, "rotating with {:?}", rot);
+            assert_eq!(&new_dial, expected_dial, "rotating with {:?}", rot);
+            dial = new_dial;
+        }
+    }
 }