From 1496f52e32378d140a3b4680764d98caf512fbf1 Mon Sep 17 00:00:00 2001
From: Josh Kingsley <josh@joshkingsley.me>
Date: Wed, 3 Dec 2025 22:16:57 +0200
Subject: Day 1 solution

---
 day1/src/main.rs | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

(limited to 'day1/src/main.rs')

diff --git a/day1/src/main.rs b/day1/src/main.rs
index 50ab8e1..1e82218 100644
--- a/day1/src/main.rs
+++ b/day1/src/main.rs
@@ -44,17 +44,16 @@ impl Dial {
 
         match rot {
             Rotation::Left(n) => {
-                if pos != 0 && *n >= pos {
-                    let quot = n.div_ceil(100);
-                    RotateResult(quot, self - *n)
-                } else {
-                    RotateResult(0, self - *n)
-                }
+                let quot: u32 = n / 100;
+                RotateResult(
+                    quot + if pos > 0 && n % 100 >= pos { 1 } else { 0 },
+                    self - *n,
+                )
             }
 
             Rotation::Right(n) => {
                 if n + pos >= 100 {
-                    let quot = n.div_ceil(100);
+                    let quot = n / 100 + (if pos + n % 100 >= 100 { 1 } else { 0 });
                     RotateResult(quot, self + *n)
                 } else {
                     RotateResult(0, self + *n)
@@ -119,6 +118,8 @@ fn main() -> anyhow::Result<()> {
 
         total_zeros += zeros;
         dial = new_dial;
+
+        eprintln!("rotation: {:?}, dial: {}, zeros: {}", rot, dial.0, zeros);
     }
 
     println!("Password: {}", exact_zeros);
@@ -197,12 +198,25 @@ mod tests {
             (Rotation::Right(1000), 10, 50),
             (Rotation::Right(48), 0, 98),
             (Rotation::Left(651), 6, 47),
+            (Rotation::Right(651), 6, 98),
+            (Rotation::Right(203), 3, 1),
+            (Rotation::Left(1), 1, 0),
+            (Rotation::Left(100), 1, 0),
+            (Rotation::Right(100), 1, 0),
         ];
 
         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);
+            assert_eq!(
+                &zeros, expected_zeros,
+                "rotating from {} with {:?}",
+                dial.0, rot
+            );
+            assert_eq!(
+                &new_dial, expected_dial,
+                "rotating from {} with {:?}",
+                dial.0, rot
+            );
             dial = new_dial;
         }
     }
-- 
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