implement minor optimizations for day 2

README.md

@@ -12,12 +12,12 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | Day | Part 1 | Part 2 |
 | :---: | :---: | :---:  |
 | [Day 1](./src/bin/01.rs) | `881.1µs` | `849.0µs` |
-| [Day 2](./src/bin/02.rs) | `225.7ms` | `250.4ms` |
+| [Day 2](./src/bin/02.rs) | `81.3ms` | `84.4ms` |
 | [Day 3](./src/bin/03.rs) | `85.9µs` | `120.1µs` |
 | [Day 4](./src/bin/04.rs) | `227.4µs` | `1.9ms` |
 | [Day 5](./src/bin/05.rs) | `159.6µs` | `21.4µs` |
 
-**Total: 480.34ms**
+**Total: 169.94ms**
 <!--- benchmarking table --->
 
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