implement day_02

src/day_02.rs

@@ -0,0 +1,123 @@
+use std::str::FromStr;
+
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[aoc_generator(day2)]
+pub fn parse_movements(input: &str) -> Vec<Movement> {
+    input
+        .split('\n')
+        .map(|input| input.parse().unwrap())
+        .collect()
+}
+
+#[aoc(day2, part1)]
+pub fn part1(input: &[Movement]) -> isize {
+    let mut state = NaiveState::default();
+    input.iter().for_each(|movement| state.movement(movement));
+    state.depth * state.horizontal_pos
+}
+
+#[aoc(day2, part2)]
+pub fn part2(input: &[Movement]) -> isize {
+    let mut state = State::default();
+    input.iter().for_each(|movement| state.movement(movement));
+    state.depth * state.horizontal_pos
+}
+
+pub struct State {
+    horizontal_pos: isize,
+    depth: isize,
+    aim: isize,
+}
+
+impl Default for State {
+    fn default() -> State {
+        State {
+            horizontal_pos: 0,
+            depth: 0,
+            aim: 0,
+        }
+    }
+}
+
+impl State {
+    fn movement(&mut self, movement: &Movement) {
+        match movement {
+            Movement::Forward(units) => {
+                self.horizontal_pos += units;
+                self.depth += units * self.aim;
+            }
+            Movement::Down(units) => self.aim += units,
+            Movement::Up(units) => self.aim -= units,
+        }
+    }
+}
+
+pub struct NaiveState {
+    horizontal_pos: isize,
+    depth: isize,
+}
+
+impl Default for NaiveState {
+    fn default() -> NaiveState {
+        NaiveState {
+            horizontal_pos: 0,
+            depth: 0,
+        }
+    }
+}
+
+impl NaiveState {
+    fn movement(&mut self, movement: &Movement) {
+        match movement {
+            Movement::Forward(units) => self.horizontal_pos += units,
+            Movement::Down(units) => self.depth += units,
+            Movement::Up(units) => self.depth -= units,
+        }
+    }
+}
+
+pub enum Movement {
+    Forward(isize),
+    Down(isize),
+    Up(isize),
+}
+
+impl FromStr for Movement {
+    type Err = ();
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if let Some(units) = s.strip_prefix("forward ") {
+            Ok(Self::Forward(units.parse().unwrap()))
+        } else if let Some(units) = s.strip_prefix("down ") {
+            Ok(Self::Down(units.parse().unwrap()))
+        } else if let Some(units) = s.strip_prefix("up ") {
+            Ok(Self::Up(units.parse().unwrap()))
+        } else {
+            Err(())
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    const EXAMPLE_INPUT: &str = "forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2";
+
+    #[test]
+    fn part1_example() {
+        let input = super::parse_movements(EXAMPLE_INPUT);
+        let result = super::part1(&input);
+        assert_eq!(result, 150);
+    }
+
+    #[test]
+    fn part2_example() {
+        let input = super::parse_movements(EXAMPLE_INPUT);
+        let result = super::part2(&input);
+        assert_eq!(result, 900);
+    }
+}

src/lib.rs

@@ -1,5 +1,6 @@
 use aoc_runner_derive::aoc_lib;
 
 pub mod day_01;
+pub mod day_02;
 
 aoc_lib! { year = 2021 }