Solution day 2

src/days/day_2.rs

@@ -0,0 +1,54 @@
+use std::fs::File;
+use std::io;
+use std::io::BufRead;
+use std::io::BufReader;
+
+/// Parses a string & returns its effect on the horizontal & vertical position/aim
+pub fn parse_ins(s: &str) -> (i32, i32) {
+    let mut parts = s.split_ascii_whitespace();
+    let command = parts.next().unwrap();
+    let num: i32 = parts.next().unwrap().parse().unwrap();
+
+    match command {
+        "forward" => (num, 0),
+        "down" => (0, num),
+        "up" => (0, -num),
+        _ => unimplemented!(),
+    }
+}
+
+pub fn part1() -> io::Result<i32> {
+    let file = File::open("input/day2")?;
+    let reader = BufReader::new(file);
+
+    let mut forward = 0;
+    let mut depth = 0;
+
+    for line in reader.lines() {
+        let (f, d) = parse_ins(&line.unwrap());
+
+        forward += f;
+        depth += d;
+    }
+
+    Ok(forward * depth)
+}
+
+pub fn part2() -> io::Result<i32> {
+    let file = File::open("input/day2")?;
+    let reader = BufReader::new(file);
+
+    let mut forward = 0;
+    let mut depth = 0;
+    let mut aim = 0;
+
+    for line in reader.lines() {
+        let (f, a) = parse_ins(&line.unwrap());
+
+        aim += a;
+        forward += f;
+        depth += aim * f;
+    }
+
+    Ok(forward * depth)
+}

src/days/mod.rs

@@ -1 +1,2 @@
 pub mod day_1;
+pub mod day_2;

src/main.rs

@@ -4,4 +4,6 @@ fn main() {
     // Day 1
     println!("Day 1, part 1: {}", days::day_1::part1().unwrap());
     println!("Day 1, part 2: {}", days::day_1::part2().unwrap());
+    println!("Day 2, part 1: {}", days::day_2::part1().unwrap());
+    println!("Day 2, part 2: {}", days::day_2::part2().unwrap());
 }