# Leetcode 341 Solution

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

## Solution

``````# """
# 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
#        """

class NestedIterator:
def __init__(self, nestedList: [NestedInteger]):
self.s = [(nestedList, 0)]

def next(self) -> int:
self.hasNext()

return self.s.pop()[0]

def hasNext(self) -> bool:
if not self.s:
return False

while self.s:
ele = self.s.pop()

if isinstance(ele[0], int):
self.s.append((ele[0], int))
return True
elif isinstance(ele[0], list):
lst, index = ele

if index == len(lst):
continue

if index < len(lst):
self.s.append((lst, index + 1))

if lst[index].isInteger():
self.s.append((lst[index].getInteger(), 0))
else:
self.s.append((lst[index].getList(), 0))
else:
raise Exception("Unexpected type '{}'!".format(type(ele[0])))

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