solve: day2

Author: tom-anders

Cargo.toml

@@ -2,7 +2,7 @@
 resolver = "2"
 members = [
     "aoc_lib/aoc_derive",
-    "aoc_lib/utils", "day1",
+    "aoc_lib/utils", "day1", "day2",
 ]
 
 [workspace.dependencies]

aoc_lib

@@ -0,0 +1,18 @@
+[package]
+name = "day2"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+aoc_derive.path = '../aoc_lib/aoc_derive'
+utils.path = '../aoc_lib/utils'
+derive_more.workspace = true
+itertools.workspace = true
+lazy-regex.workspace = true
+parse-display.workspace = true
+rayon.workspace = true
+regex.workspace = true
+num.workspace = true
+
+[dev-dependencies]
+pretty_assertions.workspace = true

day2/Cargo.toml

@@ -0,0 +1,56 @@
+use aoc_derive::aoc_main;
+use itertools::Itertools;
+use num::Integer;
+use utils::*;
+
+fn invalid(id: usize) -> bool {
+    let s = id.to_string();
+    s.len().is_even() && s[..s.len() / 2] == s[s.len() / 2..]
+}
+
+fn invalid2(id: usize) -> bool {
+    let chars = id.to_string().chars().collect_vec();
+    (1..=(chars.len() / 2))
+        .filter(|&count| chars.len().is_multiple_of(count))
+        .any(|count| chars.iter().skip(count).enumerate().all(|(i, &c)| chars[i % count] == c))
+}
+
+#[aoc_main]
+fn solve(input: Input) -> impl Into<Solution> {
+    let ranges = input.as_str().trim().split(',').map(|s| {
+        let (start, end) = s.split_once('-').unwrap();
+        start.parse::<usize>().unwrap()..=end.parse::<usize>().unwrap()
+    });
+
+    (
+        ranges.clone().flat_map(|r| r.filter(|&i| invalid(i))).sum_usize(),
+        ranges.flat_map(|r| r.filter(|&i| invalid2(i))).sum_usize(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use utils::assert_example;
+        assert_example!(
+            r#"11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124"#,
+            1227775554,
+            4174379265_usize
+        );
+
+        assert!(!invalid2(10));
+        assert!(invalid2(11));
+        assert!(invalid2(1111));
+        assert!(!invalid2(11110));
+        assert!(invalid2(10101010));
+        assert!(invalid2(123123));
+        assert!(!invalid2(1231231));
+        assert!(!invalid2(12312));
+        assert!(!invalid2(1231));
+        assert!(!invalid2(2));
+        assert!(!invalid2(1230123));
+    }
+}