minor day 4 optimization and cleanup

README.md

@@ -23,15 +23,15 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 
 | Day | Part 1 | Part 2 |
 | :---: | :---: | :---:  |
-| [Day 1](./src/bin/01.rs) | `27.7µs` | `38.2µs` |
-| [Day 2](./src/bin/02.rs) | `41.3µs` | `41.5µs` |
-| [Day 3](./src/bin/03.rs) | `119.4µs` | `114.8µs` |
-| [Day 4](./src/bin/04.rs) | `53.3µs` | `53.8µs` |
-| [Day 5](./src/bin/05.rs) | `20.5µs` | `24.3µs` |
-| [Day 6](./src/bin/06.rs) | `202.0ns` | `102.0ns` |
-| [Day 7](./src/bin/07.rs) | `131.4µs` | `136.0µs` |
-
-**Total: 0.80ms**
+| [Day 1](./src/bin/01.rs) | `35.5µs` | `34.2µs` |
+| [Day 2](./src/bin/02.rs) | `42.1µs` | `41.8µs` |
+| [Day 3](./src/bin/03.rs) | `116.8µs` | `116.1µs` |
+| [Day 4](./src/bin/04.rs) | `48.9µs` | `50.4µs` |
+| [Day 5](./src/bin/05.rs) | `20.8µs` | `24.1µs` |
+| [Day 6](./src/bin/06.rs) | `208.0ns` | `102.0ns` |
+| [Day 7](./src/bin/07.rs) | `128.7µs` | `133.9µs` |
+
+**Total: 0.79ms**
 <!--- benchmarking table --->
 
 ---

src/bin/04.rs

@@ -1,9 +1,11 @@
+use rayon::{iter::ParallelIterator, str::ParallelString};
+
 advent_of_code::solution!(4);
 
 pub fn part_one(input: &str) -> Option<u32> {
     Some(
         input
-            .lines()
+            .par_lines()
             .filter_map(winning_number_count)
             .filter(|&c| c > 0)
             .map(|c| 1 << (c - 1))
@@ -32,17 +34,16 @@ fn winning_number_count(card: &str) -> Option<u32> {
     let (_, numbers_part) = card.split_once(':')?;
     let (winning_str, have_str) = numbers_part.split_once('|')?;
     let mut winning_numbers = [false; 100];
-    for s in winning_str.split_whitespace() {
-        winning_numbers[s.parse::<usize>().ok()?] = true;
-    }
-    let mut count = 0;
-    for s in have_str.split_whitespace() {
-        let num = s.parse::<usize>().ok()?;
-        if winning_numbers[num] {
-            count += 1;
-        }
+    for num in winning_str.split_whitespace().map(|s| s.parse::<usize>()) {
+        winning_numbers[num.ok()?] = true;
     }
-    Some(count)
+    Some(
+        have_str
+            .split_whitespace()
+            .filter_map(|s| s.parse::<usize>().ok())
+            .filter(|&num| winning_numbers[num])
+            .count() as u32,
+    )
 }
 
 #[cfg(test)]