From 4aa7e9f43cd20a7b52ee33ab126918c62992bd3d Mon Sep 17 00:00:00 2001
From: Keenan Tims <ktims@gotroot.ca>
Date: Thu, 12 Dec 2024 17:56:28 -0800
Subject: [PATCH] day3: perf - branchless

---
 src/day3.rs | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/src/day3.rs b/src/day3.rs
index 75879b2..a4d0109 100644
--- a/src/day3.rs
+++ b/src/day3.rs
@@ -11,33 +11,32 @@ pub fn get_input(input: &[u8]) -> Vec<String> {
 // PROBLEM 1 solution
 #[aoc(day3, part1)]
 pub fn part1(input: &Vec<String>) -> u64 {
-    let mut sum = 0u64;
     let re = Regex::new(r"(?-u)mul\((\d+),(\d+)\)").unwrap();
-    for line in input {
-        let line = line.as_bytes();
-        for m in re.captures_iter(line) {
-            sum += u64::from_radix_10(&m[1]).0 * u64::from_radix_10(&m[2]).0;
-        }
-    }
-    sum
+    input
+        .iter()
+        .map(|line| {
+            re.captures_iter(line.as_bytes())
+                .map(|m| u64::from_radix_10(&m[1]).0 * u64::from_radix_10(&m[2]).0)
+                .sum::<u64>()
+        })
+        .sum()
 }
 
 // PROBLEM 2 solution
 #[aoc(day3, part2)]
 pub fn part2(input: &Vec<String>) -> u64 {
     let mut sum = 0u64;
-    let mut do_mul = true;
+    let mut do_mul: u64 = 1;
     let re = Regex::new(r"(?-u)(do\(\)|don't\(\)|mul\((\d+),(\d+)\))").unwrap();
     for line in input {
         let line = line.as_bytes();
         for m in re.captures_iter(line) {
             match &m[1] {
-                b"do()" => do_mul = true,
-                b"don't()" => do_mul = false,
-                _ if do_mul => {
-                    sum += u64::from_radix_10(&m[2]).0 * u64::from_radix_10(&m[3]).0;
+                b"do()" => do_mul = 1,
+                b"don't()" => do_mul = 0,
+                _ => {
+                    sum += u64::from_radix_10(&m[2]).0 * u64::from_radix_10(&m[3]).0 * do_mul;
                 }
-                _ => {}
             }
         }
     }