1 files changed, 69 insertions, 0 deletions
diff --git a/2024_rust/src/bin/day2.rs b/2024_rust/src/bin/day2.rs
new file mode 100644
index 0000000..92d288f
--- /dev/null
+++ b/2024_rust/src/bin/day2.rs
@@ -0,0 +1,69 @@
+#[derive(PartialEq, Clone, Copy)]
+enum Direction {
+    Up,
+    Down,
+    Unknown,
+}
+use Direction::*;
+
+fn is_safe(levels: &[u32]) -> bool {
+    let mut direction = Unknown;
+    for i in 0..levels.len() - 1 {
+        let [x, y] = levels[i..=i + 1] else {
+            unreachable!()
+        };
+        let (diff, d) = if x > y { (x - y, Down) } else { (y - x, Up) };
+        if direction == Unknown {
+            direction = d;
+        }
+        if diff == 0 || diff > 3 || direction != d {
+            return false;
+        }
+    }
+    return true;
+}
+
+fn p1(input: &str) -> String {
+    let mut total = 0;
+    for report in input.lines() {
+        let levels: Vec<u32> = report
+            .split_whitespace()
+            .map(|l| l.parse().unwrap())
+            .collect();
+        if is_safe(&levels) {
+            total += 1;
+        }
+    }
+
+    total.to_string()
+}
+
+fn is_safe_with_dampener(levels: &[u32]) -> bool {
+    for i in 0..levels.len() {
+        let mut levels_without_i: Vec<u32> = levels.to_vec();
+        levels_without_i.remove(i);
+        if is_safe(&levels_without_i) {
+            return true;
+        }
+    }
+    return false;
+}
+
+fn p2(input: &str) -> String {
+    let mut total = 0;
+    for report in input.lines() {
+        let levels: Vec<u32> = report
+            .split_whitespace()
+            .map(|l| l.parse().unwrap())
+            .collect();
+        if is_safe(&levels) || is_safe_with_dampener(&levels) {
+            total += 1;
+        }
+    }
+
+    total.to_string()
+}
+
+fn main() {
+    aoc2024::run_day("2", p1, p2);
+}