Update benchmark

Author: maneatingape

README.md

@@ -367,7 +367,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 10 | [Balance Bots](https://adventofcode.com/2016/day/10) | [Source](src/year2016/day10.rs) | 14 |
 | 11 | [Radioisotope Thermoelectric Generators](https://adventofcode.com/2016/day/11) | [Source](src/year2016/day11.rs) | 719 |
 | 12 | [Leonardo's Monorail](https://adventofcode.com/2016/day/12) | [Source](src/year2016/day12.rs) | 1 |
-| 13 | [A Maze of Twisty Little Cubicles](https://adventofcode.com/2016/day/13) | [Source](src/year2016/day13.rs) | 3 |
+| 13 | [A Maze of Twisty Little Cubicles](https://adventofcode.com/2016/day/13) | [Source](src/year2016/day13.rs) | 2 |
 | 14 | [One-Time Pad](https://adventofcode.com/2016/day/14) | [Source](src/year2016/day14.rs) | 71000 |
 | 15 | [Timing is Everything](https://adventofcode.com/2016/day/15) | [Source](src/year2016/day15.rs) | 1 |
 | 16 | [Dragon Checksum](https://adventofcode.com/2016/day/16) | [Source](src/year2016/day16.rs) | 1 |

src/year2016/day13.rs

@@ -35,6 +35,8 @@ pub fn parse(input: &str) -> Input {
     todo.push_back((1, 1, 0));
 
     while let Some((x, y, cost)) = todo.pop_front() {
+        // Target is at least 68 moves from the start. Since we're doing a BFS we're guaranteed
+        // to have checked all locations less than or equal to 50. 
         if x == 31 && y == 39 {
             return (cost, part_two);
         }