FlattenNestedLists.py (using queues)

class NestedIterator:
    def __init__(self, nestedList: [NestedInteger]):
        self.stack = [] #create empty stack
        self.flatten(nestedList) #flattens nested lists
    
    def flatten(self, nestedList):
        for elem in reversed(nestedList): 
            if elem.isInteger(): #check for element in lists
                self.stack.append(elem) #append the elem in stack
            else:
                self.flatten(elem.getList()) #if it is nested list then flatten and iterate

    def next(self) -> int:
        return self.stack.pop() #pop the last elem in stack

    
    def hasNext(self) -> bool:
         return len(self.stack) > 0 #checks if stack is empty or not