Zigzag Iterator

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 next repeatedly until hasNext returns false, the order of elements returned by 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?

Clarification for the follow up question - Update (2015-09-18): The "Zigzag" order is not clearly defined and is ambiguous for k > 2 cases. If "Zigzag" does not look right to you, replace "Zigzag" with "Cyclic". For example, given the following input:

[1,2,3]
[4,5,6,7]
[8,9]

It should return [1,4,8,2,5,9,3,6,7].

public class ZigzagIterator {
    
    List<Iterator<Integer>> iters = new ArrayList<>();
    int count = 0;

    public ZigzagIterator(List<List<Integer>> lists) {
        for (List<Integer> v : lists) {
            if (!v.isEmpty()) iters.add(v.iterator());
        }
    }

    public int next() {
        int x = iters.get(count).next();
        if (!iters.get(count).hasNext())
            iters.remove(count);
        else
            count++;

        if (iters.size() != 0)
            count %= iters.size();
        return x;
    }

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

/**
 * Your ZigzagIterator object will be instantiated and called as such:
 * ZigzagIterator i = new ZigzagIterator(v1, v2); while (i.hasNext()) v[f()] =
 * i.next();
 */