Year 2025 Day 2

Author: maneatingape

README.md

@@ -78,6 +78,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | Day | Problem | Solution | Benchmark (μs) |
 | --- | --- | --- | --: |
 | 1 | [Secret Entrance](https://adventofcode.com/2025/day/1) | [Source](src/year2025/day01.rs) | 25 |
+| 2 | [Gift Shop](https://adventofcode.com/2025/day/2) | [Source](src/year2025/day02.rs) | 40000 |
 
 ## 2024
 

benches/benchmark.rs

@@ -95,5 +95,5 @@ benchmark!(year2024
 );
 
 benchmark!(year2025
-    day01
+    day01, day02
 );

src/lib.rs

@@ -74,5 +74,5 @@ library!(year2024 "Locate the Chief Historian in time for the big Christmas slei
 );
 
 library!(year2025 "Finish the North Pole decorations in time for Christmas."
-    day01
+    day01, day02
 );

src/main.rs

@@ -141,5 +141,5 @@ run!(year2024
 );
 
 run!(year2025
-    day01
+    day01, day02
 );

src/year2025/day02.rs

@@ -0,0 +1,46 @@
+use crate::util::iter::*;
+use crate::util::parse::*;
+use std::io::Write as _;
+
+type Input = (u64, u64);
+
+pub fn parse(input: &str) -> Input {
+    let mut id = Vec::new();
+    let mut part_one = 0;
+    let mut part_two = 0;
+
+    for [from, to] in input.iter_unsigned::<u64>().chunk::<2>() {
+        for number in from..=to {
+            id.clear();
+            let _unused = write!(&mut id, "{number}");
+            let digits = id.len();
+
+            let half = digits / 2;
+            if id[0..half] == id[half..] {
+                part_one += number;
+                part_two += number;
+                continue;
+            }
+
+            for size in 1..=digits / 2 {
+                if digits % size == 0 {
+                    let first = &id[0..size];
+                    if (size..digits).step_by(size).all(|i| &id[i..i + size] == first) {
+                        part_two += number;
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    (part_one, part_two)
+}
+
+pub fn part1(input: &Input) -> u64 {
+    input.0
+}
+
+pub fn part2(input: &Input) -> u64 {
+    input.1
+}

tests/test.rs

@@ -87,5 +87,5 @@ test!(year2024
 );
 
 test!(year2025
-    day01
+    day01, day02
 );

tests/year2025/day02.rs

@@ -0,0 +1,15 @@
+use aoc::year2025::day02::*;
+
+const EXAMPLE: &str = "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 1227775554);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 4174379265);
+}