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# Time: O(1) per peek(), next(), hasNext()

# Space: O(1)

class PeekingIterator(object):

def __init__(self, iterator):

"""

Initialize your data structure here.

:type iterator: Iterator

"""

self.iterator = iterator

self.val_ = None

self.has_next_ = iterator.hasNext()

self.has_peeked_ = False

def peek(self):

"""

Returns the next element in the iteration without advancing the iterator.

:rtype: int

"""

if not self.has_peeked_:

self.has_peeked_ = True

self.val_ = self.iterator.next()

return self.val_

def next(self):

"""

:rtype: int

"""

self.val_ = self.peek()

self.has_peeked_ = False

self.has_next_ = self.iterator.hasNext()

return self.val_

def hasNext(self):

"""

:rtype: bool

"""

return self.has_next_