341. Flatten Nested List Iterator【M】【42】

Given a nested list of integers, implement an iterator to flatten it.
Each element is either an integer, or a list -- whose elements may also be integers or other lists.
Example 1:

Given the list

[[1,1],2,[1,1]]

,
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be:

[1,1,2,1,1]

.

Example 2:

Given the list

[1,[4,[6]]]

,
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be:

[1,4,6]

.

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# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
#class NestedInteger(object):
#    def isInteger(self):
#        """
#        @return True if this NestedInteger holds a single integer, rather than a nested list.
#        :rtype bool
#        """
#
#    def getInteger(self):
#        """
#        @return the single integer that this NestedInteger holds, if it holds a single integer
#        Return None if this NestedInteger holds a nested list
#        :rtype int
#        """
#
#    def getList(self):
#        """
#        @return the nested list that this NestedInteger holds, if it holds a nested list
#        Return None if this NestedInteger holds a single integer
#        :rtype List[NestedInteger]
#        """

class NestedIterator(object):

def __init__(self, nestedList):

l = nestedList
self.res = []

if not l:
return

while l != []:
i = l.pop(0)
if i.isInteger():
self.res += i.getInteger(),
else:
l = i.getList() + l

"""
Initialize your data structure here.
:type nestedList: List[NestedInteger]
"""

def next(self):
return self.res.pop(0)
"""
:rtype: int
"""

def hasNext(self):
return self.res != []
"""
:rtype: bool
"""

# Your NestedIterator object will be instantiated and called as such:
# i, v = NestedIterator(nestedList), []
# while i.hasNext(): v.append(i.next())