Day 2

input/02-test.txt

@@ -0,0 +1,6 @@
+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2

src/bin/02.rs

@@ -0,0 +1,59 @@
+fn main() {
+    let mut pos = State::default();
+    pos.apply(input());
+    println!("First solution: {:?} => {}", pos, pos.position * pos.depth);
+
+    let mut pos = State::default();
+    pos.apply_new(input());
+    println!("Second solution: {:?} => {}", pos, pos.position * pos.depth);
+}
+
+#[derive(Debug, Default)]
+struct State {
+    position: i32,
+    depth: i32,
+    aim: i32,
+}
+
+impl State {
+    fn apply(&mut self, instructions: impl Iterator<Item = Instruction>) {
+        for i in instructions {
+            match i.direction {
+                "up" => self.depth -= i.distance,
+                "down" => self.depth += i.distance,
+                "forward" => self.position += i.distance,
+                d => panic!("unknown direction: {}", d),
+            }
+        }
+    }
+
+    fn apply_new(&mut self, instructions: impl Iterator<Item = Instruction>) {
+        for i in instructions {
+            match i.direction {
+                "up" => self.aim -= i.distance,
+                "down" => self.aim += i.distance,
+                "forward" => {
+                    self.position += i.distance;
+                    self.depth += self.aim * i.distance;
+                }
+                d => panic!("unknown direction: {}", d),
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+struct Instruction {
+    direction: &'static str,
+    distance: i32,
+}
+
+fn input() -> impl Iterator<Item = Instruction> {
+    include_str!("../../input/02.txt")
+        .lines()
+        .filter_map(|l| l.split_once(" "))
+        .map(|(d, n)| Instruction {
+            direction: d,
+            distance: n.parse().unwrap(),
+        })
+}