Solve 03

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),
+}