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

src/common/geometry.rs

@@ -1,3 +1,17 @@
+#[derive(Hash, PartialEq, Eq, Debug)]
+pub struct Point2(pub u64, pub u64);
+
+impl Point2 {
+    pub fn from_line(line: &str, separator: char) -> Self {
+        let p: Vec<u64> = line.split(separator).map(|s| s.parse().unwrap()).collect();
+        Self(p[0], p[1])
+    }
+
+    pub fn rect_area(&self, other: &Self) -> u64 {
+        (self.0.abs_diff(other.0) + 1) * (self.1.abs_diff(other.1) + 1)
+    }
+}
+
 #[derive(Hash, PartialEq, Eq, Debug)]
 pub struct Point3(pub u64, pub u64, pub u64);
 

src/main.rs

@@ -10,4 +10,5 @@ fn main() {
     solvers::run(solvers::trash_compactor::TrashCompactor {});
     // Laboratories
     solvers::run(solvers::playground::Playground::new(None));
+    solvers::run(solvers::movie_theater::MovieTheater {});
 }

src/solvers.rs

@@ -6,6 +6,7 @@ use std::path;
 use std::path::Path;
 
 pub mod cafeteria;
+pub mod movie_theater;
 pub mod playground;
 pub mod printing_department;
 pub mod trash_compactor;

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)
+    }
+}