day-12/src/main.rs

@@ -8,6 +8,10 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let location = simulate_ship_movement(&actions);
     println!("{}", location.0.abs() + location.1.abs());
 
+    // Part 2
+    let location = simulate_waypoint_movement(&actions);
+    println!("{}", location.0.abs() + location.1.abs());
+
     Ok(())
 }
 
@@ -136,6 +140,48 @@ fn simulate_ship_movement(actions: &Vec<Action>) -> (i64, i64) {
     coords
 }
 
+fn simulate_waypoint_movement(actions: &Vec<Action>) -> (i64, i64) {
+    let mut waypoint = (1, 10);
+    let mut ship = (0, 0);
+
+    for action in actions {
+        match *action {
+            Action::North(amount) => {
+                waypoint.0 += amount as i64;
+            }
+            Action::South(amount) => {
+                waypoint.0 -= amount as i64;
+            }
+            Action::East(amount) => {
+                waypoint.1 += amount as i64;
+            }
+            Action::West(amount) => {
+                waypoint.1 -= amount as i64;
+            }
+            Action::Left(amount) => match amount % 360 {
+                0 => {}
+                90 => waypoint = (waypoint.1, -waypoint.0),
+                180 => waypoint = (-waypoint.0, -waypoint.1),
+                270 => waypoint = (-waypoint.1, waypoint.0),
+                _ => panic!("Only 90 degree turns allowed"),
+            },
+            Action::Right(amount) => match amount % 360 {
+                0 => {}
+                90 => waypoint = (-waypoint.1, waypoint.0),
+                180 => waypoint = (-waypoint.0, -waypoint.1),
+                270 => waypoint = (waypoint.1, -waypoint.0),
+                _ => panic!("Only 90 degree turns allowed"),
+            },
+            Action::Forward(amount) => {
+                ship.0 += waypoint.0 * amount as i64;
+                ship.1 += waypoint.1 * amount as i64;
+            }
+        }
+    }
+
+    ship
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -158,4 +204,22 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn test_simple2() -> Result<(), Box<dyn std::error::Error>> {
+        let input = indoc!(
+            "F10
+             N3
+             F7
+             R90
+             F11
+            "
+        );
+
+        let actions = parse_actions(&input)?;
+        let location = simulate_waypoint_movement(&actions);
+        assert_eq!(location.0.abs() + location.1.abs(), 286);
+
+        Ok(())
+    }
 }