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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,
}
#[derive(Debug, Clone, Copy)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ActionKind {
Move(Direction),
@ -114,45 +114,42 @@ impl Ship {
self.x.abs() + self.y.abs()
}
fn process(&mut self, action: Action) {
match action.kind {
ActionKind::Move(dir) => self.forward(dir, action.arg),
ActionKind::Right => {
debug_assert!(action.arg % 90 == 0, "only right angles are supported");
let quarters = action.arg / 90;
let new_dir = Self::CLOCKWISE_DIRECTIONS
.iter()
fn find_direction<I>(iter: I, quarters: usize, current_direction: Direction) -> Direction
where
I: Iterator<Item = Direction>,
I: std::clone::Clone,
{
iter
// this is litteraly a circle, reaching West and turning 90 degrees right means
// facing North again
.cycle()
// find our current ship direction
.skip_while(|dir| **dir != self.direction)
.skip_while(|dir| *dir != current_direction)
// 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
.unwrap();
self.direction = *new_dir;
.unwrap()
}
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");
let quarters = action.arg / 90;
let quarters = (action.arg / 90) as usize;
let new_dir = Self::CLOCKWISE_DIRECTIONS
.iter()
// same thing as above, but reverse direction first!
.rev()
.cycle()
.skip_while(|dir| **dir != self.direction)
.nth(quarters as usize)
.unwrap();
let directions_iter = Self::CLOCKWISE_DIRECTIONS.iter().copied();
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),