Zigzag Iterator 解答

Question

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?

Solution

This solution is suitable for k vectors.

 public class ZigzagIterator {
     private List<Iterator> list;

     public ZigzagIterator(List<Integer> v1, List<Integer> v2) {
         list = new ArrayList<Iterator>();
         if (v1.iterator().hasNext())
             list.add(v1.iterator());
         if (v2.iterator().hasNext())
             list.add(v2.iterator());
     }

     public int next() {
         Iterator<Integer> current = list.remove(0);
         int result = current.next();
         if(current.hasNext())
             list.add(current);
         return result;
     }

     public boolean hasNext() {
         return list.size() > 0 ? true : false;
     }
 }

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