From 9192d658468427bd3cc7cfeaa994c02a13bea29f Mon Sep 17 00:00:00 2001
From: Lars Martens <lars@martens.red>
Date: Tue, 3 Dec 2024 07:49:46 +0100
Subject: [PATCH] Solve 03

---
 Cargo.lock    | 45 +++++++++++++++++++++++++++++++++++++++
 Cargo.toml    |  1 +
 input/03-test |  1 +
 src/bin/03.rs | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 106 insertions(+)
 create mode 100644 input/03-test
 create mode 100644 src/bin/03.rs

diff --git a/Cargo.lock b/Cargo.lock
index d72c3eb..bbb663d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,6 +14,15 @@ dependencies = [
  "zerocopy",
 ]
 
+[[package]]
+name = "aho-corasick"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "allocator-api2"
 version = "0.2.20"
@@ -35,6 +44,7 @@ dependencies = [
  "glam",
  "itertools",
  "rayon",
+ "regex",
 ]
 
 [[package]]
@@ -188,6 +198,12 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "memchr"
+version = "2.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
+
 [[package]]
 name = "once_cell"
 version = "1.20.2"
@@ -232,6 +248,35 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "regex"
+version = "1.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b544ef1b4eac5dc2db33ea63606ae9ffcfac26c1416a2806ae0bf5f56b201191"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "809e8dc61f6de73b46c85f4c96486310fe304c434cfa43669d7b40f711150908"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b15c43186be67a4fd63bee50d0303afffcef381492ebe2c5d87f324e1b8815c"
+
 [[package]]
 name = "strsim"
 version = "0.10.0"
diff --git a/Cargo.toml b/Cargo.toml
index 2c594d7..1a442ea 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,3 +9,4 @@ cached = "0.46.1"
 glam = "0.29.2"
 itertools = "0.12.0"
 rayon = "1.8.0"
+regex = "1.11.1"
diff --git a/input/03-test b/input/03-test
new file mode 100644
index 0000000..30032cb
--- /dev/null
+++ b/input/03-test
@@ -0,0 +1 @@
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
diff --git a/src/bin/03.rs b/src/bin/03.rs
new file mode 100644
index 0000000..27f20b9
--- /dev/null
+++ b/src/bin/03.rs
@@ -0,0 +1,59 @@
+use aoc::*;
+use regex::{Captures, Regex};
+
+const INPUT: &str = include_str!("../../input/03");
+
+fn main() {
+    assert_example!(part1, "03-test", 161);
+    println!("Part 1: {}", part1(INPUT));
+    assert_example!(part2, "03-test", 48);
+    println!("Part 2: {}", part2(INPUT));
+}
+
+fn part1(input: &str) -> i64 {
+    parse(input)
+        .into_iter()
+        .filter_map(|i| match i {
+            Instruction::Mul(a, b) => Some(a * b),
+            Instruction::Do | Instruction::Dont => None,
+        })
+        .sum()
+}
+
+fn part2(input: &str) -> i64 {
+    let mut sum = 0;
+    let mut enabled = true;
+    for instruction in parse(input) {
+        match instruction {
+            Instruction::Do => enabled = true,
+            Instruction::Dont => enabled = false,
+            Instruction::Mul(a, b) if enabled => {
+                sum += a * b;
+            }
+            Instruction::Mul(_, _) => (),
+        }
+    }
+    sum
+}
+
+fn parse(input: &str) -> Vec<Instruction> {
+    let regex = Regex::new(r#"(mul\((\d+),(\d+)\)|don't\(\)|do\(\))"#).unwrap();
+    regex.captures_iter(input).map(parse_instruction).collect()
+}
+
+fn parse_instruction(c: Captures) -> Instruction {
+    if c[0].starts_with("mul") {
+        let (a, b) = (c[2].parse().unwrap(), c[3].parse().unwrap());
+        Instruction::Mul(a, b)
+    } else if c[0].starts_with("don") {
+        Instruction::Dont
+    } else {
+        Instruction::Do
+    }
+}
+
+enum Instruction {
+    Do,
+    Dont,
+    Mul(i64, i64),
+}