281. Zigzag Iterator

Given two 1d vectors, implement an iterator to return their elements alternately.

Example:

Input:

v1 = [1,2]
v2 = [3,4,5,6] 
Output:

 
[1,3,2,4,5,6]
Explanation:


 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 :
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:

Input:

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

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

.