next()

Iterator Adaptors

Iterator adaptors takes ownership of the iterator and returns another kind of iterator, which allows chaining. The commonly used adaptors are map(), filter(),

The chain of iterators is lazy

Aggregation Functions

fn main() {
    use Direction::*;
    println!(
        "{:?}",
        dir_reduc(&[NORTH, SOUTH, EAST, WEST, NORTH, WEST])
    );
}

#[derive(PartialEq, Eq, Debug, Clone)]
enum Direction {
    NORTH,
    SOUTH,
    EAST,
    WEST,
}

impl Direction {
    fn opposite(&self) -> Direction {
        match self {
            Direction::NORTH => Direction::SOUTH,
            Direction::SOUTH => Direction::NORTH,
            Direction::EAST => Direction::WEST,
            Direction::WEST => Direction::EAST,
        }
    }
}

fn dir_reduc(arr: &[Direction]) -> Vec<Direction> {
    let mut res: Vec<Direction> = vec![arr[0].clone()];
    let mut del = 0;
    for i in 1..arr.len() {
        let dir = &arr[i];
        if *dir == arr[i - 1].opposite() {
            res.pop();
            del += 1;
        } else {
            res.push(dir.clone())
        }
    }
    if del > 0 {
        return dir_reduc(&res);
    }
    res
}

## [NORTH, WEST]