From cc2a0fa1c2762407317adb76fd1135b1db9a2ada Mon Sep 17 00:00:00 2001
From: Connor Glosser <me@rayhem.dev>
Date: Mon, 2 Dec 2024 13:46:58 -0500
Subject: [PATCH] Solve 2024 day 02

---
 src/lib/solutions/year_2024/day_01.rs |   1 +
 src/lib/solutions/year_2024/day_02.rs | 107 ++++++++++++++++++++++++++
 src/lib/solutions/year_2024/mod.rs    |   2 +
 3 files changed, 110 insertions(+)
 create mode 100644 src/lib/solutions/year_2024/day_02.rs

diff --git a/src/lib/solutions/year_2024/day_01.rs b/src/lib/solutions/year_2024/day_01.rs
index 47fa541..306b479 100644
--- a/src/lib/solutions/year_2024/day_01.rs
+++ b/src/lib/solutions/year_2024/day_01.rs
@@ -50,6 +50,7 @@ fn sorted_lists(input: &str) -> (Vec<i32>, Vec<i32>) {
     (left.into_sorted_vec(), right.into_sorted_vec())
 }
 
+#[allow(unused_imports)]
 mod tests {
     use super::*;
 
diff --git a/src/lib/solutions/year_2024/day_02.rs b/src/lib/solutions/year_2024/day_02.rs
new file mode 100644
index 0000000..a20b752
--- /dev/null
+++ b/src/lib/solutions/year_2024/day_02.rs
@@ -0,0 +1,107 @@
+use crate::utils::solution::Solution;
+
+/// Puzzle: https://adventofcode.com/2024/day/2/
+pub struct Day02 {}
+
+impl Solution for Day02 {
+    fn part_one(&self, input: &str) -> Option<String> {
+        Some(
+            reports(input)
+                .iter()
+                .filter(|r| r.status() == Status::Safe)
+                .count()
+                .to_string(),
+        )
+    }
+
+    fn part_two(&self, input: &str) -> Option<String> {
+        Some(
+            reports(input)
+                .iter()
+                .filter(|r| r.status() != Status::Unsafe)
+                .count()
+                .to_string(),
+        )
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+enum Status {
+    Safe,
+    Dampened,
+    Unsafe,
+}
+
+#[derive(Debug)]
+struct Report {
+    levels: Vec<i32>,
+}
+
+impl Report {
+    fn status(&self) -> Status {
+        fn is_safe<T: Iterator<Item = i32> + Clone>(mut values: T) -> bool {
+            values.clone().all(|delta| (1..=3).contains(&delta))
+                || values.all(|delta| (-3..=-1).contains(&delta))
+        }
+
+        let deltas = (0..self.levels.len()).map(|i| {
+            let reduced = self
+                .levels
+                .iter()
+                .enumerate()
+                .filter(move |(n, _)| i != *n)
+                .map(|(_, x)| x);
+
+            reduced.clone().zip(reduced.skip(1)).map(|(a, b)| b - a)
+        });
+
+        if is_safe(
+            self.levels
+                .iter()
+                .zip(self.levels.iter().skip(1))
+                .map(|(a, b)| b - a),
+        ) {
+            Status::Safe
+        } else if deltas.clone().any(is_safe) {
+            Status::Dampened
+        } else {
+            Status::Unsafe
+        }
+    }
+}
+
+impl From<&str> for Report {
+    fn from(value: &str) -> Self {
+        Report {
+            levels: value
+                .split_ascii_whitespace()
+                .flat_map(str::parse::<i32>)
+                .collect(),
+        }
+    }
+}
+
+fn reports(input: &str) -> Vec<Report> {
+    input.lines().map(Into::into).collect()
+}
+
+#[allow(unused_imports)]
+mod tests {
+    use itertools::Itertools;
+
+    use super::*;
+
+    #[test]
+    fn example() {
+        const INPUT: &str = "7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9
+";
+        let day02 = Day02 {};
+        assert_eq!(day02.part_one(INPUT), Some("2".to_string()));
+        assert_eq!(day02.part_two(INPUT), Some("4".to_string()));
+    }
+}
diff --git a/src/lib/solutions/year_2024/mod.rs b/src/lib/solutions/year_2024/mod.rs
index eac2e6f..7a725ba 100644
--- a/src/lib/solutions/year_2024/mod.rs
+++ b/src/lib/solutions/year_2024/mod.rs
@@ -1,10 +1,12 @@
 use super::DayAssociations;
 
 pub mod day_01;
+pub mod day_02;
 
 pub fn solutions() -> DayAssociations {
     let associations: Vec<(i32, super::BoxedSolution)> = vec![
         (1, Box::new(day_01::Day01 {})),
+        (2, Box::new(day_02::Day02 {})),
     ];
 
     associations.into_iter().collect()