Peekable Iterator

Implement an iterator of a list of integers nums where

• peek() returns the next element, without moving the iterator
• next() polls the next element in the iterator
• hasnext() which returns whether the next element exists

Constraints

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

https://binarysearch.com/problems/Peekable-Iterator

Examples

Example 1

Input

• methods = ['constructor', 'peek', 'next', 'hasnext', 'peek', 'next', 'hasnext']
• arguments = [[[1, 2]], [], [], [], [], [], []]

Output

• answer = [None, 1, 1, True, 2, 2, False]

Explanation

• First we create a PeekableIterator with values [1, 2]
• We peek the next element which is 1
• We poll the next element which is 1
• We check if the next element exists, which it does since 2 is next in the iterator.
• We peek the next element which is 2
• We poll the next element which is 2
• We check if the next element exists which it doesn’t

Solution