1 files changed, 144 insertions, 0 deletions
diff --git a/12/src/main.rs b/12/src/main.rs
new file mode 100644
index 0000000..33999a9
--- /dev/null
+++ b/12/src/main.rs
@@ -0,0 +1,144 @@
+use advent_lib::prelude::*;
+
+//use std::convert::TryFrom;
+
+#[derive(Debug)]
+struct ShipState {
+  x_offset: i64, // positive is east
+  y_offset: i64, // positive is north
+  heading: i64, // 0 is east; 90 is north
+}
+
+#[derive(Debug)]
+struct NavState {
+  waypoint_x_offset: i64,
+  waypoint_y_offset: i64,
+  ship_x_offset: i64,
+  ship_y_offset: i64,
+}
+
+
+impl ShipState {
+  fn new() -> ShipState {
+    ShipState {
+      x_offset: 0,
+      y_offset: 0,
+      heading: 0,
+    }
+  }
+}
+
+impl NavState {
+  fn new() -> NavState {
+    NavState {
+      waypoint_x_offset: 10,
+      waypoint_y_offset: 1,
+      ship_x_offset: 0,
+      ship_y_offset: 0,
+    }
+  }
+}
+
+
+fn main() -> Result<()> {
+  let mut args = std::env::args();
+  if args.len() != 2 {
+    eprintln!("Usage: advent input");
+  }
+  let _ = args.next();
+  let filename = args.next().unwrap();
+
+  let input = advent_lib::read_lines_file(&filename)?;
+
+  let mut ship = ShipState::new();
+  let mut nav = NavState::new();
+
+  for line in &input {
+    let (command, parameter_str) = line.split_at(1);
+    let parameter = parameter_str.parse::<i64>()?;
+
+    match command {
+      "N" => {
+        ship.y_offset += parameter;
+        nav.waypoint_y_offset += parameter;
+      },
+      "S" => {
+        ship.y_offset -= parameter;
+        nav.waypoint_y_offset -= parameter;
+      },
+      "E" => {
+        ship.x_offset += parameter;
+        nav.waypoint_x_offset += parameter;
+      },
+      "W" => {
+        ship.x_offset -= parameter;
+        nav.waypoint_x_offset -= parameter;
+      },
+      "L" => {
+        ship.heading = (ship.heading + parameter) % 360;
+
+        rotate_waypoint(&mut nav, parameter);
+      },
+      "R" => {
+        ship.heading = (ship.heading - parameter + 360) % 360;
+
+        rotate_waypoint(&mut nav, -parameter);
+      },
+      "F" => {
+        while ship.heading < 0 {
+          ship.heading += 360;
+        }
+        ship.heading = ship.heading % 360;
+
+        if ship.heading == 0 {
+          ship.x_offset += parameter;
+        } else if ship.heading == 90 {
+          ship.y_offset += parameter;
+        } else if ship.heading == 180 {
+          ship.x_offset -= parameter;
+        } else if ship.heading == 270 {
+          ship.y_offset -= parameter;
+        }
+
+        nav.ship_x_offset += parameter * nav.waypoint_x_offset;
+        nav.ship_y_offset += parameter * nav.waypoint_y_offset;
+      },
+      _ => { },
+    }
+  }
+
+  let ship_distance = ship.x_offset.abs() + ship.y_offset.abs();
+  let nav_distance = nav.ship_x_offset.abs() + nav.ship_y_offset.abs();
+  println!("{}", ship_distance);
+  println!("{}", nav_distance);
+
+  Ok(())
+}
+
+
+fn rotate_waypoint(nav: &mut NavState, parameter: i64) {
+  let mut rotation = parameter;
+  while rotation < 0 {
+    rotation += 360;
+  }
+  rotation = rotation % 360;
+
+  if rotation == 90 {
+    // counterclockwise
+    let x_tmp = nav.waypoint_x_offset;
+    let y_tmp = nav.waypoint_y_offset;
+    nav.waypoint_y_offset = x_tmp;
+    nav.waypoint_x_offset = -y_tmp;
+  } else if rotation == 270 {
+    // clockwise
+    let x_tmp = nav.waypoint_x_offset;
+    let y_tmp = nav.waypoint_y_offset;
+    nav.waypoint_y_offset = -x_tmp;
+    nav.waypoint_x_offset = y_tmp;
+  } else if rotation == 180 {
+    let x_tmp = nav.waypoint_x_offset;
+    let y_tmp = nav.waypoint_y_offset;
+    nav.waypoint_x_offset = -x_tmp;
+    nav.waypoint_y_offset = -y_tmp;
+  }
+}