341. Flatten Nested List Iterator

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

class NestedIterator:
    def __init__(self, nestedList: [NestedInteger]):
        self.cache = [item for item in self._flatten(nestedList)]
        self.cur = 0
        self.length = len(self.cache)

    def _flatten(self, node):
        if not node:
            return

        if isinstance(node, list):
            items = node
        elif node.isInteger():
            items = []
            yield node
        else:
            items = node.getList()

        for item in items:
            if item.isInteger():
                yield item.getInteger()
            else:
                for children in item.getList():
                    for child in self._flatten(children):
                        yield child

    def next(self) -> int:
        i = self.cur
        self.cur += 1
        return self.cache[i]

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


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

Python
