simply neighbors iterator after refactor for day 16

README.md

@@ -47,9 +47,9 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 13](./src/bin/13.rs) | `12.3µs` | `15.9µs` |
 | [Day 14](./src/bin/14.rs) | `25.0µs` | `4.5ms` |
 | [Day 15](./src/bin/15.rs) | `20.4µs` | `85.9µs` |
-| [Day 16](./src/bin/16.rs) | `223.2µs` | `10.9ms` |
+| [Day 16](./src/bin/16.rs) | `177.4µs` | `8.2ms` |
 
-**Total: 18.14ms**
+**Total: 15.39ms**
 <!--- benchmarking table --->
 
 ---

src/bin/16.rs

@@ -84,12 +84,10 @@ impl Grid {
         dir: Direction,
         tile: Tile,
     ) -> impl Iterator<Item = (Coordinate, Direction, Tile)> + '_ {
-        std::iter::once(tile.next(dir))
-            .flatten()
-            .filter_map(move |dir| {
-                self.move_in_dir(coord, dir)
-                    .map(|c| (c, dir, self.get_tile(c)))
-            })
+        tile.next(dir).filter_map(move |dir| {
+            self.move_in_dir(coord, dir)
+                .map(|c| (c, dir, self.get_tile(c)))
+        })
     }
 
     pub fn get_tile(&self, coord: Coordinate) -> Tile {