Simpler and faster brute force approach

Author: maneatingape

README.md

@@ -58,7 +58,7 @@ Improvements to solutions are always appreciated. Please see the
 ## Performance
 
 Benchmarks are measured using the built-in `cargo bench` tool run on an [Apple M2 Max][apple-link].
-All 250 solutions from 2024 to 2015 complete sequentially in **580 milliseconds**.
+All 250 solutions from 2024 to 2015 complete sequentially in **573 milliseconds**.
 Interestingly 84% of the total time is spent on just 9 solutions.
 Performance is reasonable even on older hardware, for example a 2011 MacBook Pro with an
 [Intel i7-2720QM][intel-link] processor takes 3.5 seconds to run the same 250 solutions.
@@ -67,7 +67,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 
 | Year | [2015](#2015) | [2016](#2016) | [2017](#2017) | [2018](#2018) | [2019](#2019) | [2020](#2020) | [2021](#2021) | [2022](#2022) | [2023](#2023) | [2024](#2024) |
 | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
-| Benchmark (ms) | 24 | 119 | 88 | 35 | 16 | 270 | 9 | 8 | 6 | 5 |
+| Benchmark (ms) | 17 | 119 | 88 | 35 | 16 | 270 | 9 | 8 | 6 | 4 |
 
 ## 2024
 
@@ -368,7 +368,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 3 | [Perfectly Spherical Houses in a Vacuum](https://adventofcode.com/2015/day/3) | [Source](src/year2015/day03.rs) | 95 |
 | 4 | [The Ideal Stocking Stuffer](https://adventofcode.com/2015/day/4) | [Source](src/year2015/day04.rs) | 14000 |
 | 5 | [Doesn't He Have Intern-Elves For This?](https://adventofcode.com/2015/day/5) | [Source](src/year2015/day05.rs) | 38 |
-| 6 | [Probably a Fire Hazard](https://adventofcode.com/2015/day/6) | [Source](src/year2015/day06.rs) | 6572 |
+| 6 | [Probably a Fire Hazard](https://adventofcode.com/2015/day/6) | [Source](src/year2015/day06.rs) | 386 |
 | 7 | [Some Assembly Required](https://adventofcode.com/2015/day/7) | [Source](src/year2015/day07.rs) | 27 |
 | 8 | [Matchsticks](https://adventofcode.com/2015/day/8) | [Source](src/year2015/day08.rs) | 5 |
 | 9 | [All in a Single Night](https://adventofcode.com/2015/day/9) | [Source](src/year2015/day09.rs) | 34 |