Zigzag Iterator

Source

• leetcode: 281

Given two 1d vectors, implement an iterator to return their elements alternately.
For example, given two 1d vectors:
v1 = [1, 2]v2 = [3, 4, 5, 6]
By calling 【i】next repeatedly until 【i】hasNext returns false, the order of
elements returned by 【i】next should be: [1, 3, 2, 4, 5, 6].
Follow up: What if you are given k 1d vectors? How well can your code be
extended to such cases?

Java

//适用于k vectors
public class ZigzagIterator {
    LinkedList<Iterator> list;
    public ZigzagIterator(List<Integer> v1, List<Integer> v2) {
        list = new LinkedList<Iterator>();
        if(!v1.isEmpty()) list.add(v1.iterator());
        if(!v2.isEmpty()) list.add(v2.iterator());
    }

    public int next() {
        Iterator poll = list.remove();
        int result = (Integer)poll.next();
        if(poll.hasNext()) list.add(poll);
        return result;
    }

    public boolean hasNext() {
        return !list.isEmpty();
    }
}