Two-Dimensional List Iterator

Implement an iterator of two-dimensional list of integers lists.

• next() polls the next element in the iterator, iterating over each row in lists
• hasnext() which returns whether the next element exists

For example:

it = TwoDimensionalIterator([[1, 2],[3, 4],[5]])
it.next() == 1
it.next() == 2
it.next() == 3
it.hasnext() == True
it.next() == 4
it.next() == 5
it.hasnext() == False

Constraints

• n ≤ 100,000 where n is the number of calls to next and hasnext

Notes

• Your iterator should use \(\mathcal{O}(1)\) extra space.

https://binarysearch.com/problems/Two-Dimensional-List-Iterator

Examples

Example 1

Input

• methods = ['constructor', 'next', 'next', 'next', 'hasnext', 'next', 'next', 'hasnext']
• arguments = [[[[1, 2], [3, 4], [5]]], [], [], [], [], [], [], []]

Output

• answer = [None, 1, 2, 3, True, 4, 5, False]

Solution