@Override
    public Integer next() {
        if (!hasNext()) {
            throw new IllegalArgumentException();
        }
        int data = vector.get(currentList).get(currentPos);
        currentPos++;
        if (currentPos == vector.get(currentList).size()) {
            currentPos = 0;
            currentList++;
        }
        return data;
    }
Date 10/10/2016
@author Tushar Roy

Implement an iterator to flatten a 2d vector.

https://leetcode.com/problems/flatten-2d-vector/
src/com/interview/linklist/Flatten2DList.java