Day 02

Author: m0lson84

README.md

@@ -194,20 +194,24 @@ By default, `cargo time` does not write to the readme. In order to do so, append
 
 <!--- advent_readme_stars table --->
 
+## 2025 Results
+
 |                     Day                      | Part 1 | Part 2 |
 | :------------------------------------------: | :----: | :----: |
 | [Day 1](https://adventofcode.com/2025/day/1) |   ⭐   |   ⭐   |
+| [Day 2](https://adventofcode.com/2025/day/2) |   ⭐   |   ⭐   |
 
 <!--- advent_readme_stars table --->
 
-## Benchmarks
-
 <!--- benchmarking table --->
 
-|           Day            |  Part 1  |  Part 2  |
-| :----------------------: | :------: | :------: |
-| [Day 1](./src/bin/01.rs) | `82.6µs` | `93.5µs` |
+## Benchmarks
+
+|           Day            |  Part 1  |  Part 2   |
+| :----------------------: | :------: | :-------: |
+| [Day 1](./src/bin/01.rs) | `51.1µs` | `38.7µs`  |
+| [Day 2](./src/bin/02.rs) | `27.1ms` | `117.0ms` |
 
-**Total: 0.18ms**
+**Total: 144.19ms**
 
 <!--- benchmarking table --->

data/examples/02.txt

@@ -0,0 +1 @@
+11-22,95-115,998-1012,1188511880-1188511890,222220-222224, 1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124

src/bin/02.rs

@@ -0,0 +1,74 @@
+advent_of_code::solution!(2);
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let mut result = 0;
+    for range in input.split(',') {
+        let (first_id, last_id) = get_ids(range)?;
+        result += (first_id..=last_id)
+            .filter(|&id| is_invalid(id.to_string()))
+            .sum::<u64>();
+    }
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let mut result = 0;
+    for range in input.split(',') {
+        let (first_id, last_id) = get_ids(range)?;
+        result += (first_id..=last_id)
+            .filter(|&id| is_invalid_strict(id.to_string()))
+            .sum::<u64>();
+    }
+    Some(result)
+}
+
+fn get_ids(range: &str) -> Option<(u64, u64)> {
+    let ids: Vec<&str> = range.trim().split('-').collect();
+    let first = ids[0].parse::<u64>().ok()?;
+    let last = ids[1].parse::<u64>().ok()?;
+    Some((first, last))
+}
+
+fn is_invalid(id: String) -> bool {
+    let length = id.len();
+    if !length.is_multiple_of(2) {
+        return false;
+    }
+
+    let mid = length / 2;
+    id[0..mid] == id[mid..]
+}
+
+fn is_invalid_strict(id: String) -> bool {
+    let length = id.len();
+    for i in 1..=length / 2 {
+        if !length.is_multiple_of(i) {
+            continue;
+        }
+
+        let candidate = &id[0..i];
+        if candidate.repeat(length / i) == id {
+            return true;
+        }
+    }
+
+    false
+}
+
+#[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(1227775554));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(4174379265));
+    }
+}