leetcode

Flatten Nested List Iterator

Flatten Nested List Iterator

Generators Version

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# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
#class NestedInteger(object):
#    def isInteger(self):
#        """
#        @return True if this NestedInteger holds a single integer, rather than a nested list.
#        :rtype bool
#        """
#
#    def getInteger(self):
#        """
#        @return the single integer that this NestedInteger holds, if it holds a single integer
#        Return None if this NestedInteger holds a nested list
#        :rtype int
#        """
#
#    def getList(self):
#        """
#        @return the nested list that this NestedInteger holds, if it holds a nested list
#        Return None if this NestedInteger holds a single integer
#        :rtype List[NestedInteger]
#        """
class NestedIterator(object):
    def __init__(self, nestedList):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        self.ret = []
        def flat(List):
            for x in List:
                if x.isInteger():
                    yield x.getInteger()
                else:
                    for y in flat(x.getList()):
                        yield y
        self.ret = flat(nestedList)
    def next(self):
        """
        :rtype: int
        """
        return self.value
    def hasNext(self):
        """
        :rtype: bool
        """
        try:
            self.value = next(self.ret)
            return True
        except StopIteration:
            return False
# Your NestedIterator object will be instantiated and called as such:
# i, v = NestedIterator(nestedList), []
# while i.hasNext(): v.append(i.next())

Stack Version

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# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
#class NestedInteger(object):
#    def isInteger(self):
#        """
#        @return True if this NestedInteger holds a single integer, rather than a nested list.
#        :rtype bool
#        """
#
#    def getInteger(self):
#        """
#        @return the single integer that this NestedInteger holds, if it holds a single integer
#        Return None if this NestedInteger holds a nested list
#        :rtype int
#        """
#
#    def getList(self):
#        """
#        @return the nested list that this NestedInteger holds, if it holds a nested list
#        Return None if this NestedInteger holds a single integer
#        :rtype List[NestedInteger]
#        """
class NestedIterator(object):
    def __init__(self, nestedList):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        self.stack = nestedList[::-1]
    def next(self):
        """
        :rtype: int
        """
        return self.stack.pop().getInteger()
    def hasNext(self):
        """
        :rtype: bool
        """
        while self.stack:
            top = self.stack[-1]
            if top.isInteger():
                return True
            self.stack = self.stack[:-1] + top.getList()[::-1]
        return False
# Your NestedIterator object will be instantiated and called as such:
# i, v = NestedIterator(nestedList), []
# while i.hasNext(): v.append(i.next())

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