[LeetCode][Python]Flatten Nested List Iterator

 Flatten Nested List Iterator

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].

https://leetcode.com/problems/flatten-nested-list-iterator/

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展平嵌套的list。

从调用的方式来看，总会调用到最后，所以在构造函数中递归展开所有的数放到一位数组中。

另一种方式是把nested list压到栈中，需要的时候再从栈中拿。

注意需要调用注释中的isInteger()，getInteger()和getList()三个方法。

# """
# 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):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        self.__list = []
        self.__index = 0
        self.__getList(nestedList)
        
    def __getList(self, nestedList):
        for item in nestedList:
            if item.isInteger():
                self.__list.append(item.getInteger())
            else:
                self.__getList(item.getList())

    def next(self):
        """
        :rtype: int
        """
        res = self.__list[self.__index]
        self.__index += 1
        return res

    def hasNext(self):
        """
        :rtype: bool
        """
        if(self.__index < len(self.__list)):
            return True
        return False