281. Zigzag Iterator

public class ZigzagIterator {

    List<List<Integer>> lists = new ArrayList<>();
    Queue<int[]> q = new LinkedList<>();
    public ZigzagIterator(List<Integer> v1, List<Integer> v2) {
        lists.add(v1);
        lists.add(v2);
        for(int i = 0; i < lists.size(); i++)
        {
            List<Integer> list = lists.get(i);
            if(list.size() > 0) q.offer(new int[]{i, 0});
        }
    }

    public int next() {
        if(!hasNext()) return -1;
        int[] poll = q.poll();
        int val = lists.get(poll[0]).get(poll[1]);
        if(lists.get(poll[0]).size() > poll[1] + 1)
        {
            poll[1] += 1;
            q.offer(poll);
        }
        return val;
    }

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

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