2024 day 2

Author: ictrobot

crates/year2024/src/day02.rs

@@ -0,0 +1,56 @@
+use utils::array::ArrayVec;
+use utils::prelude::*;
+
+/// Checking sequences of numbers.
+#[derive(Clone, Debug)]
+pub struct Day02 {
+    reports: Vec<ArrayVec<u32, 8>>,
+}
+
+impl Day02 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        Ok(Self {
+            reports: parser::u32().repeat_arrayvec(b' ', 1).parse_lines(input)?,
+        })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> usize {
+        self.reports
+            .iter()
+            .filter(|&r| Self::is_safe(r.iter().copied()))
+            .count()
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> usize {
+        self.reports
+            .iter()
+            .filter(|&r| {
+                if Self::is_safe(r.iter().copied()) {
+                    return true;
+                }
+
+                (0..r.len())
+                    .any(|i| Self::is_safe(r.iter().take(i).chain(r.iter().skip(i + 1)).copied()))
+            })
+            .count()
+    }
+
+    #[inline]
+    fn is_safe(iter: impl Iterator<Item = u32> + Clone) -> bool {
+        let mut w = iter.clone().zip(iter.skip(1));
+
+        w.clone().all(|(a, b)| (1..=3).contains(&a.wrapping_sub(b)))
+            || w.all(|(a, b)| (1..=3).contains(&b.wrapping_sub(a)))
+    }
+}
+
+examples!(Day02 -> (usize, usize) [
+    {input: "7 6 4 2 1", part1: 1, part2: 1},
+    {input: "1 2 7 8 9", part1: 0, part2: 0},
+    {input: "9 7 6 2 1", part1: 0, part2: 0},
+    {input: "1 3 2 4 5", part1: 0, part2: 1},
+    {input: "8 6 4 4 1", part1: 0, part2: 1},
+    {input: "1 3 6 7 9", part1: 1, part2: 1},
+]);

crates/year2024/src/lib.rs

@@ -3,4 +3,5 @@
 
 utils::year!(2024 => year2024, ${
     1 => day01::Day01,
+    2 => day02::Day02,
 });