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2020: day12: refacto part 1 directions iterator

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This commit is contained in:
Antoine Martin 2020-12-12 14:41:46 +01:00
parent fa879c367c
commit 1be8717564
1 changed files with 28 additions and 31 deletions
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53
aoc2020/src/day12.rs
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@ -35,7 +35,7 @@ enum Direction {
West, West,
} }
#[derive(Debug, Clone, Copy)] #[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ActionKind { enum ActionKind {
Move(Direction), Move(Direction),
@ -114,45 +114,42 @@ impl Ship {
self.x.abs() + self.y.abs() self.x.abs() + self.y.abs()
} }
fn process(&mut self, action: Action) { fn find_direction<I>(iter: I, quarters: usize, current_direction: Direction) -> Direction
match action.kind { where
ActionKind::Move(dir) => self.forward(dir, action.arg), I: Iterator<Item = Direction>,
I: std::clone::Clone,
ActionKind::Right => { {
debug_assert!(action.arg % 90 == 0, "only right angles are supported"); iter
let quarters = action.arg / 90;
let new_dir = Self::CLOCKWISE_DIRECTIONS
.iter()
// this is litteraly a circle, reaching West and turning 90 degrees right means // this is litteraly a circle, reaching West and turning 90 degrees right means
// facing North again // facing North again
.cycle() .cycle()
// find our current ship direction // find our current ship direction
.skip_while(|dir| **dir != self.direction) .skip_while(|dir| *dir != current_direction)
// skip as many quarters as needed // skip as many quarters as needed
.nth(quarters as usize) .nth(quarters)
// we can unwrap safely because we called .cycle() on a non empty iterator // we can unwrap safely because we called .cycle() on a non empty iterator
.unwrap(); .unwrap()
self.direction = *new_dir;
} }
ActionKind::Left => { fn process(&mut self, action: Action) {
match action.kind {
ActionKind::Move(dir) => self.forward(dir, action.arg),
ActionKind::Right | ActionKind::Left => {
debug_assert!(action.arg % 90 == 0, "only right angles are supported"); debug_assert!(action.arg % 90 == 0, "only right angles are supported");
let quarters = action.arg / 90; let quarters = (action.arg / 90) as usize;
let new_dir = Self::CLOCKWISE_DIRECTIONS let directions_iter = Self::CLOCKWISE_DIRECTIONS.iter().copied();
.iter()
// same thing as above, but reverse direction first!
.rev()
.cycle()
.skip_while(|dir| **dir != self.direction)
.nth(quarters as usize)
.unwrap();
self.direction = *new_dir; let new_dir = if action.kind == ActionKind::Left {
// go through cardinal directions the other way around, anti-clockwise
Ship::find_direction(directions_iter.rev(), quarters, self.direction)
} else {
Ship::find_direction(directions_iter, quarters, self.direction)
};
self.direction = new_dir;
} }
ActionKind::Forward => self.forward(self.direction, action.arg), ActionKind::Forward => self.forward(self.direction, action.arg),