251. Flatten 2D Vector

Design and implement an iterator to flatten a 2d vector. It should support the following operations: next and hasNext .

 

Example:

Vector2D iterator = new Vector2D([[1,2],[3],[4]]);
iterator.next(); // return 1
iterator.next(); // return 2
iterator.next(); // return 3
iterator.hasNext(); // return true
iterator.hasNext(); // return true
iterator.next(); // return 4
iterator.hasNext(); // return false

 

Notes:

1. Please remember to RESET your class variables declared in Vector2D, as static/class variables are persisted across multiple test cases . Please see here for more details.
2. You may assume that next() call will always be valid, that is, there will be at least a next element in the 2d vector when next() is called.

 

Follow up:

As an added challenge, try to code it using only iterators in C++ or iterators in Java .