-
Notifications
You must be signed in to change notification settings - Fork 0
/
284. Peeking Iterator.py
67 lines (60 loc) · 1.87 KB
/
284. Peeking Iterator.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
# Below is the interface for Iterator, which is already defined for you.
#
# class Iterator:
# def __init__(self, nums):
# """
# Initializes an iterator object to the beginning of a list.
# :type nums: List[int]
# """
#
# def hasNext(self):
# """
# Returns true if the iteration has more elements.
# :rtype: bool
# """
#
# def next(self):
# """
# Returns the next element in the iteration.
# :rtype: int
# """
class PeekingIterator:
def __init__(self, iterator):
"""
Initialize your data structure here.
:type iterator: Iterator
"""
self._iterator = iterator
self._peeked_value = None
def peek(self):
"""
Returns the next element in the iteration without advancing the iterator.
:rtype: int
"""
if self._peeked_value is None:
if not self._iterator.hasNext():
raise StopIteration()
self._peeked_value = self._iterator.next()
return self._peeked_value
def next(self):
"""
:rtype: int
"""
if self._peeked_value is not None:
to_return = self._peeked_value
self._peeked_value = None
return to_return
if not self._iterator.hasNext():
raise StopIteration()
# Otherwise, we need to return a new value.
return self._iterator.next()
def hasNext(self):
"""
:rtype: bool
"""
return self._peeked_value is not None or self._iterator.hasNext()
# Your PeekingIterator object will be instantiated and called as such:
# iter = PeekingIterator(Iterator(nums))
# while iter.hasNext():
# val = iter.peek() # Get the next element but not advance the iterator.
# iter.next() # Should return the same value as [val].