[341. Flatten Nested List Iterator] #leetcode

341_1017.py

class NestedIterator(object):

    def __init__(self, nestedList):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        def gen(nestedList):
            for x in nestedList:
                if x.isInteger():
                    yield x.getInteger()
                else:
                    for y in gen(x.getList()):
                        yield y
        self.gen = gen(nestedList)

    def next(self):
        """
        :rtype: int
        """
        return self.value    

    def hasNext(self):
        """
        :rtype: bool
        """
        try:
            self.value = next(self.gen)
            return True
        except StopIteration:
            return False
          
          
          
class NestedIterator(object):

    def __init__(self, nestedList):
        self.stack = [[nestedList, 0]]

    def next(self):
        self.hasNext()
        nestedList, i = self.stack[-1]
        self.stack[-1][1] += 1
        return nestedList[i].getInteger()
            
    def hasNext(self):
        s = self.stack
        while s:
            nestedList, i = s[-1]
            if i == len(nestedList):
                s.pop()
            else:
                x = nestedList[i]
                if x.isInteger():
                    return True
                s[-1][1] += 1
                s.append([x.getList(), 0])
        return False