[2025] Solution for Day 2

Author: kfarnung

2025/src/bin/day02.rs

@@ -0,0 +1,16 @@
+use aoc2025::days::day02::{part1, part2};
+use std::env;
+use std::fs;
+use std::process;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 2 {
+        println!("Missing required arguments");
+        process::exit(1);
+    }
+
+    let contents = fs::read_to_string(&args[1]).expect("Something went wrong");
+    println!("Part 1: {}", part1(&contents));
+    println!("Part 2: {}", part2(&contents));
+}

2025/src/days.rs

@@ -1 +1,2 @@
-pub mod day01;
+pub mod day01;
+pub mod day02;

2025/src/days/day02.rs

@@ -0,0 +1,80 @@
+use std::str::FromStr;
+
+pub fn part1(contents: &str) -> i64 {
+    let mut sum = 0;
+    for (start, end) in parse_data(contents) {
+        for i in start..=end {
+            let num_str = i.to_string();
+            let split = num_str.split_at(num_str.len() / 2);
+            if split.0 == split.1 {
+                sum += i;
+            }
+        }
+    }
+    sum
+}
+
+pub fn part2(contents: &str) -> i64 {
+    let mut sum = 0;
+    for (start, end) in parse_data(contents) {
+        for i in start..=end {
+            let num_str = i.to_string();
+            if match_pattern(&num_str) {
+                sum += i;
+            }
+        }
+    }
+    sum
+}
+
+fn parse_data(contents: &str) -> Vec<(i64, i64)> {
+    contents
+        .trim()
+        .split(',')
+        .map(|range| {
+            let mut bounds = range.split('-').map(|n| i64::from_str(n).unwrap());
+            let start = bounds.next().unwrap();
+            let end = bounds.next().unwrap();
+            (start, end)
+        })
+        .collect()
+}
+
+fn match_pattern(s: &str) -> bool {
+    for i in 1..=s.len() / 2 {
+        if s.len() % i != 0 {
+            continue;
+        }
+
+        let comparison = &s[0..i];
+        for j in (i..s.len()).step_by(i) {
+            let end = j + i;
+            if &s[j..end] != comparison {
+                break;
+            }
+            if end == s.len() {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part1() {
+        let content = "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124";
+
+        assert_eq!(part1(&content), 1227775554);
+    }
+
+    #[test]
+    fn test_part2() {
+        let content = "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124";
+
+        assert_eq!(part2(&content), 4174379265);
+    }
+}

2025/tests/day02.rs

@@ -0,0 +1,13 @@
+use aoc2025::days::day02::{part1, part2};
+
+#[test]
+fn test_part1() {
+    let content = std::include_str!("../../private/inputs/2025/day02.txt");
+    assert_eq!(part1(&content), 19605500130);
+}
+
+#[test]
+fn test_part2() {
+    let content = std::include_str!("../../private/inputs/2025/day02.txt");
+    assert_eq!(part2(&content), 36862281418);
+}