3rd day

Author: majcn

data/examples/03.txt

@@ -0,0 +1 @@
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))

src/bin/03.rs

@@ -0,0 +1,79 @@
+advent_of_code::solution!(3);
+
+use advent_of_code::maneatingape::parse::*;
+use regex::Regex;
+
+enum Command {
+    Enable,
+    Disable,
+    Multiply(u32, u32),
+}
+
+fn parse_data(input: &str) -> Vec<Command> {
+    let mut commands = vec![];
+
+    let mul_re = Regex::new(r"^mul\((\d{1,3}),(\d{1,3})\)").unwrap();
+
+    for i in 0..input.len() {
+        if input[i..].starts_with("mul") {
+            if let Some(m) = mul_re.captures(&input[i..]) {
+                let [x, y] = m.extract().1.map(|x| x.unsigned());
+                commands.push(Command::Multiply(x, y));
+            }
+        } else if input[i..].starts_with("do()") {
+            commands.push(Command::Enable);
+        } else if input[i..].starts_with("don't()") {
+            commands.push(Command::Disable);
+        }
+    }
+
+    commands
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let data = parse_data(input);
+
+    let result = data
+        .into_iter()
+        .map(|c| match c {
+            Command::Multiply(x, y) => x * y,
+            _ => 0,
+        })
+        .sum();
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let data = parse_data(input);
+
+    let mut enabled = true;
+
+    let mut result = 0;
+    for c in data {
+        match c {
+            Command::Multiply(x, y) => result += if enabled { x * y } else { 0 },
+            Command::Enable => enabled = true,
+            Command::Disable => enabled = false,
+        }
+    }
+
+    Some(result)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(161));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(48));
+    }
+}