solve: day9

Author: tom-anders

Cargo.toml

@@ -2,7 +2,7 @@
 resolver = "2"
 members = [
     "aoc_lib/aoc_derive",
-    "aoc_lib/utils", "day1", "day2", "day3", "day4", "day5", "day6", "day7", "day8",
+    "aoc_lib/utils", "day1", "day2", "day3", "day4", "day5", "day6", "day7", "day8", "day9",
 ]
 
 [workspace.dependencies]

day9/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "day9"
+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

day9/src/main.rs

@@ -0,0 +1,83 @@
+use std::ops::RangeInclusive;
+
+use aoc_derive::aoc_main;
+use itertools::Itertools;
+use utils::math::Vec2D;
+use utils::*;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Rect {
+    range_x: RangeInclusive<i64>,
+    range_y: RangeInclusive<i64>,
+}
+
+impl Rect {
+    fn new(a: &Vec2D, b: &Vec2D) -> Self {
+        Self { range_x: a.x.min(b.x)..=a.x.max(b.x), range_y: a.y.min(b.y)..=a.y.max(b.y) }
+    }
+
+    fn area(&self) -> i64 {
+        (self.range_x.try_len().unwrap() * self.range_y.try_len().unwrap()) as i64
+    }
+
+    fn intersects(&self, (v1, v2): &(Vec2D, Vec2D)) -> bool {
+        let vx = v1.x.min(v2.x)..=v1.x.max(v2.x);
+        let vy = v1.y.min(v2.y)..=v1.y.max(v2.y);
+
+        if vx.end() <= self.range_x.start() || vx.start() >= self.range_x.end() {
+            return false;
+        }
+
+        if vy.end() <= self.range_y.start() || vy.start() >= self.range_y.end() {
+            return false;
+        }
+
+        true
+    }
+}
+
+fn part2(poly: &[Vec2D]) -> i64 {
+    let vertices: Vec<(Vec2D, Vec2D)> = poly.iter().copied().circular_tuple_windows().collect();
+
+    poly.iter()
+        .tuple_combinations()
+        .map(|(a, b)| Rect::new(a, b))
+        .filter(|rect| vertices.iter().all(|v| !rect.intersects(v)))
+        .map(|r| r.area())
+        .max()
+        .unwrap()
+}
+
+#[aoc_main]
+fn solve(input: Input) -> impl Into<Solution> {
+    let poly = input
+        .lines()
+        .map(|line| {
+            let (x, y) = extract_numbers(line).collect_tuple().unwrap();
+            Vec2D::new(x, y)
+        })
+        .collect_vec();
+
+    (poly.iter().tuple_combinations().map(|(a, b)| Rect::new(a, b).area()).max(), part2(&poly))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_examples() {
+        use utils::assert_example;
+        assert_example!(
+            r#"7,1
+11,1
+11,7
+9,7
+9,5
+2,5
+2,3
+7,3"#,
+            50,
+            24
+        );
+    }
+}