leetcode 341. Flatten Nested List Iterator

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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):
        self.stack = [[nestedList, 0]]

    def next(self):
        self.hasNext()
        nestedList, i = self.stack[-1]
        self.stack[-1][1] += 1
        return nestedList[i].getInteger()
            
    def hasNext(self):
        s = self.stack
        while s:
            nestedList, i = s[-1]
            if i == len(nestedList):
                s.pop()
            else:
                x = nestedList[i]
                if x.isInteger():
                    return True
                s[-1][1] += 1
                s.append([x.getList(), 0])
        return False
# class NestedIterator(object):

#     def __init__(self, nestedList):
#         """
#         Initialize your data structure here.
#         :type nestedList: List[NestedInteger]
#         """
#         self._ind = 0
#         self._nest = self._flat(nestedList)
        
#     def _flat(self,nestlist):
#         res = []
#         stack = [(nestlist,0)]
#         while stack:
#             nest,i = stack.pop()
#             if i >= len(nest):
#                 continue
#             tmp = nest[i]
#             stack.append((nest,i+1))
#             if tmp.isInteger():
#                 res.append(tmp)
#             else:
#                 stack.append((tmp,0))
#         return res

#     def next(self):
#         """
#         :rtype: int
#         """
#         i = self._ind
#         self._ind += 1
#         return self._nest[i]
            
        

#     def hasNext(self):
#         """
#         :rtype: bool
#         """
#         return self._ind < len(self._nest)

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