Flatten Nested List Iterator

nested_iterator.py

"""
Description:
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.

Use API below to implement the class:
"""
#class NestedInteger:
#    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]
#        """
"""
Examples:
Input: [[1,1],2,[1,1]]
Output: [1,1,2,1,1]

Input: [1,[4,[6]]]
Output: [1,4,6]
"""

class NestedIterator:
    def __init__(self, nestedList):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        self.stack = [iter(nestedList)]
        self.cur = None
        self.__update__()

    def __update__(self):
        while self.stack and self.cur == None:
            curIter = self.stack[-1]
            try:
                nested = next(curIter)
                if nested.isInteger():
                    self.cur = nested.getInteger()
                else:
                    self.stack.append(iter(nested.getList()))
            except StopIteration:
                self.stack.pop()
                continue

    def next(self):
        """
        :rtype: int
        """
        value = self.cur
        self.cur = None
        self.__update__()
        return value

    def hasNext(self):
        """
        :rtype: bool
        """
        return self.cur != None