题目
Given an Iterator class interface with methods: next() and hasNext(), design and implement a PeekingIterator that support the peek() operation – it essentially peek() at the element that will be returned by the next call to next().
解题思路
记录当前的peek，next会返回当前的peek，并且更新peek为下一个数
代码
class PeekingIterator:
def __init__(self, iterator):
"""
Initialize your data structure here.
:type iterator: Iterator
"""
self.it = iterator
self.peeknum = self.it.next() if self.it.hasNext() else None
def peek(self):
"""
Returns the next element in the iteration without advancing the iterator.
:rtype: int
"""
return self.peeknum
def next(self):
"""
:rtype: int
"""
ret = self.peeknum
self.peeknum = self.it.next() if self.it.hasNext() else None
return ret
def hasNext(self):
"""
:rtype: bool
"""
return self.peeknum is not None
