很笨的把两个list当数组用了 还把list复制了一遍

list自己的iterator就可以了 而且有个很好的方法就是两个iterator每次swap就可以了 不用判断上个是输出的谁 

public class ZigzagIterator {
    Iterator<Integer> it1, it2;

    public ZigzagIterator(List<Integer> v1, List<Integer> v2) {
        it1 = v1.iterator();
        it2 = v2.iterator();
    }

    public int next() {
        if ( it1.hasNext() ){
            Iterator <Integer> temp = it1;
            it1 = it2;
            it2 = temp;
        }
        return it2.next();
        
    }
    public boolean hasNext() {
        return it1.hasNext() || it2.hasNext();
    }
}

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