Add Day 9 Part 1 solution - find largest rectangle from red tiles

README.md

@@ -19,8 +19,9 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 6](./src/bin/06.rs) | `118.7µs` | `124.8µs` |
 | [Day 7](./src/bin/07.rs) | `91.8µs` | `72.4µs` |
 | [Day 8](./src/bin/08.rs) | `11.2ms` | `9.8ms` |
+| [Day 9](./src/bin/09.rs) | `114.1µs` | `-` |
 
-**Total: 23.40ms**
+**Total: 23.51ms**
 <!--- benchmarking table --->
 
 ---

data/examples/09.txt

@@ -0,0 +1,10 @@
+7,1
+11,1
+11,7
+9,7
+9,5
+2,5
+2,3
+7,3
+
+

src/bin/09.rs

@@ -0,0 +1,54 @@
+advent_of_code::solution!(9);
+
+use itertools::Itertools;
+
+fn parse_coords(input: &str) -> Vec<(i64, i64)> {
+    input
+        .lines()
+        .filter_map(|line| {
+            let line = line.trim();
+            if line.is_empty() {
+                return None;
+            }
+            let (x, y) = line.split_once(',')?;
+            Some((x.trim().parse().ok()?, y.trim().parse().ok()?))
+        })
+        .collect()
+}
+
+fn rectangle_area(p1: (i64, i64), p2: (i64, i64)) -> u64 {
+    let width = (p2.0 - p1.0).abs() + 1;
+    let height = (p2.1 - p1.1).abs() + 1;
+    (width * height) as u64
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let coords = parse_coords(input);
+
+    coords
+        .iter()
+        .tuple_combinations()
+        .map(|(&p1, &p2)| rectangle_area(p1, p2))
+        .max()
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(50));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}