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2020: day12: refacto turn directions

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This commit is contained in:
Antoine Martin 2020-12-12 15:48:15 +01:00
parent e19ca07c6b
commit 442f4621fb
1 changed files with 29 additions and 28 deletions
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57
aoc2020/src/day12.rs
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@ -51,12 +51,17 @@ enum Direction {
West,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum TurnDirection {
Left,
Right,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ActionKind {
Move(Direction),
Left,
Right,
Turn(TurnDirection),
Forward,
}
@ -87,8 +92,8 @@ impl std::str::FromStr for Action {
'E' => ActionKind::Move(Direction::East),
'W' => ActionKind::Move(Direction::West),
'L' => ActionKind::Left,
'R' => ActionKind::Right,
'L' => ActionKind::Turn(TurnDirection::Left),
'R' => ActionKind::Turn(TurnDirection::Right),
'F' => ActionKind::Forward,
@ -154,14 +159,14 @@ impl Ship {
match action.kind {
ActionKind::Move(dir) => self.forward(dir, action.arg),
ActionKind::Right | ActionKind::Left => {
ActionKind::Turn(turn_dir) => {
debug_assert!(action.arg % 90 == 0, "only right angles are supported");
let quarters = (action.arg / 90) as usize;
let directions_iter = Self::CLOCKWISE_DIRECTIONS.iter().copied();
let new_dir = if action.kind == ActionKind::Left {
let new_dir = if turn_dir == TurnDirection::Left {
// go through cardinal directions the other way around, anti-clockwise
Ship::find_direction(directions_iter.rev(), quarters, self.direction)
} else {
@ -184,31 +189,12 @@ impl Ship {
Direction::East => self.waypoint.x += action.arg as i64,
},
ActionKind::Left => {
ActionKind::Turn(turn_dir) => {
debug_assert!(action.arg % 90 == 0, "only right angles are supported");
let quarters = (action.arg / 90) as usize % 4;
let quadrants = (action.arg / 90) as usize % 4;
for _ in 0..quarters {
let x = self.waypoint.x as i64;
let y = self.waypoint.y as i64;
self.waypoint.x = y;
self.waypoint.y = -x;
}
}
ActionKind::Right => {
debug_assert!(action.arg % 90 == 0, "only right angles are supported");
let quarters = (action.arg / 90) as usize % 4;
for _ in 0..quarters {
let x = self.waypoint.x as i64;
let y = self.waypoint.y as i64;
self.waypoint.x = -y;
self.waypoint.y = x;
}
self.waypoint.turn(turn_dir, quadrants);
}
ActionKind::Forward => {
@ -257,6 +243,21 @@ impl Waypoint {
(west_east, north_south)
}
fn turn(&mut self, turn_dir: TurnDirection, quadrants: usize) {
for _ in 0..quadrants {
let mut x = self.x;
let mut y = self.y;
match turn_dir {
TurnDirection::Left => x = -x,
TurnDirection::Right => y = -y,
}
self.x = y;
self.y = x;
}
}
}
#[cfg(test)]