Solve 02

src/bin/02.rs

@@ -0,0 +1,62 @@
+use aoc::*;
+
+const INPUT: &str = include_str!("../../input/02");
+
+fn main() {
+    println!("Part 1: {}", part1(INPUT));
+    println!("Part 2: {}", part2(INPUT));
+}
+
+#[test]
+fn example() {
+    assert_example!(part1, "02-test", 1227775554);
+    assert_example!(part2, "02-test", 4174379265);
+}
+
+fn part1(input: &str) -> usize {
+    parse_input(input)
+        .map(|r| r.invalid_id_sum(is_doubled))
+        .sum()
+}
+
+fn part2(input: &str) -> usize {
+    parse_input(input)
+        .map(|r| r.invalid_id_sum(is_repeated))
+        .sum()
+}
+
+fn is_doubled(id: usize) -> bool {
+    let id = id.to_string();
+    let (hi, lo) = id.split_at(id.len() / 2);
+    hi == lo
+}
+
+fn is_repeated(id: usize) -> bool {
+    let id = id.to_string();
+
+    (1..id.len())
+        .map(|prefix_len| &id[0..prefix_len])
+        .any(|prefix| id.trim_start_matches(prefix).is_empty())
+}
+
+struct Range {
+    from: usize,
+    to: usize,
+}
+
+impl Range {
+    fn parse(s: &str) -> Self {
+        let (from, to) = s.split_once('-').unwrap();
+        let from = from.trim().parse().unwrap();
+        let to = to.trim().parse().unwrap();
+        Self { from, to }
+    }
+
+    fn invalid_id_sum(self, is_invalid: fn(usize) -> bool) -> usize {
+        (self.from..=self.to).filter(|&n| is_invalid(n)).sum()
+    }
+}
+
+fn parse_input(input: &str) -> impl Iterator<Item = Range> + use<'_> {
+    input.split(',').map(Range::parse)
+}