class NestedIterator:
    def __init__(self, nestedList: list):
        self.flat: list = self.flattener(nestedList)
        self.index = 0

    def flattener(self, nestedList) -> list:
        flat: list = []
        for item in nestedList:
            if isinstance(item, list):
                flat.extend(self.flattener(item))
            else:
                flat.append(item)
        return flat

    def next(self) -> int | None:
        if self.hasNext():
            self.index += 1
            return self.flat[self.index - 1]

    def hasNext(self) -> bool:
        size = len(self.flat)
        return self.index < size


initial: list = [1, 2, [3, 4], 5, [6, 7, [8, [9, 10]]]]
# test: list = [[1, 1], 2, [1, 1]]
# flatten: NestedIterator = NestedIterator(test)
# flat: list = []
# while flatten.hasNext():
#     flat.append(flatten.next())
# print(flat)
#
# i, v = NestedIterator(nestedList), []
# while i.hasNext(): v.append(i.next())
flatten2, res = NestedIterator(initial), []
while flatten2.hasNext():
    res.append(flatten2.next())
print(res)