Day 01

Author: m0lson84

README.md

@@ -189,3 +189,25 @@ By default, `cargo time` does not write to the readme. In order to do so, append
 > [!NOTE]
 > Please note that these are not _scientific_ benchmarks, understand them as a fun approximation. 😉 Timings, especially
 > in the microseconds range, might change a bit between invocations.
+
+## Results
+
+<!--- advent_readme_stars table --->
+
+|                     Day                      | Part 1 | Part 2 |
+| :------------------------------------------: | :----: | :----: |
+| [Day 1](https://adventofcode.com/2025/day/1) |   ⭐   |   ⭐   |
+
+<!--- advent_readme_stars table --->
+
+## Benchmarks
+
+<!--- benchmarking table --->
+
+|           Day            |  Part 1  |  Part 2  |
+| :----------------------: | :------: | :------: |
+| [Day 1](./src/bin/01.rs) | `82.6µs` | `93.5µs` |
+
+**Total: 0.18ms**
+
+<!--- benchmarking table --->

data/examples/01.txt

@@ -0,0 +1,10 @@
+L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82

src/bin/.keep

@@ -0,0 +1,78 @@
+advent_of_code::solution!(1);
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let mut position: i64 = 50;
+    let mut result: u64 = 0;
+    for turn in input.lines() {
+        let (direction, distance) = parse_rotation(turn)?;
+
+        position = apply_rotation(position, direction, distance);
+
+        if position == 0 {
+            result += 1;
+        }
+    }
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let mut position: i64 = 50;
+    let mut result: u64 = 0;
+
+    for turn in input.lines() {
+        let (direction, distance) = parse_rotation(turn)?;
+
+        // Count complete loops (each loop crosses 0 once)
+        let complete_loops = distance / 100;
+        result += complete_loops as u64;
+
+        // Check if the partial rotation crosses 0
+        let remaining = distance % 100;
+        let crosses_zero = match direction {
+            'R' => position + remaining >= 100,
+            'L' => position - remaining <= 0 && position > 0,
+            _ => false,
+        };
+
+        if crosses_zero {
+            result += 1;
+        }
+
+        // Update position for next iteration
+        position = apply_rotation(position, direction, distance);
+    }
+
+    Some(result)
+}
+
+fn apply_rotation(position: i64, direction: char, distance: i64) -> i64 {
+    match direction {
+        'R' => (position + distance).rem_euclid(100),
+        'L' => (position - distance).rem_euclid(100),
+        _ => position,
+    }
+}
+
+fn parse_rotation(line: &str) -> Option<(char, i64)> {
+    let direction = line.chars().next()?;
+    let distance: i64 = line[1..].parse().ok()?;
+    Some((direction, distance))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(3));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(6));
+    }
+}