Add solution for "Day 9: Movie Theater", part 1

src/solvers/movie_theater.rs

@@ -0,0 +1,44 @@
+use crate::common::geometry::Point2;
+use crate::solvers::Solver;
+use std::io::BufRead;
+
+pub struct MovieTheater {}
+
+impl MovieTheater {
+    const POINT_SPLIT_CHAR: char = ',';
+
+    // Collects all red tile coordinates.
+    fn red_tiles<R: BufRead>(reader: R) -> Vec<Point2> {
+        let mut red_tiles = Vec::new();
+        for line in reader.lines().map_while(Result::ok) {
+            red_tiles.push(Point2::from_line(&line, Self::POINT_SPLIT_CHAR));
+        }
+        red_tiles
+    }
+
+    // Maps the closest pairs of junction boxes to their distances, up to the maximum number of
+    // connections.
+    fn largest_rectangle(red_tiles: &Vec<Point2>) -> u64 {
+        let mut max = 0;
+        for i in 0..red_tiles.len() {
+            let (_, right) = red_tiles.split_at(i + 1);
+            for b in right {
+                let a = red_tiles[i].rect_area(b);
+                if max < a {
+                    max = a;
+                }
+            }
+        }
+        max
+    }
+}
+
+impl Solver for MovieTheater {
+    const PUZZLE_INDEX: u8 = 9;
+    const PUZZLE_NAME: &'static str = "Movie Theater";
+
+    fn process_data<R: BufRead>(&self, reader: R) -> (u64, u64) {
+        let red_tiles = Self::red_tiles(reader);
+        (Self::largest_rectangle(&red_tiles), 0)
+    }
+}