[LeetCode]341. 扁平化嵌套列表迭代器(Flatten Nested List Iterator)

题目描述

给定一个嵌套的整型列表。设计一个迭代器,使其能够遍历这个整型列表中的所有整数。

列表中的项或者为一个整数,或者是另一个列表。

示例 1:

输入: [[1,1],2,[1,1]]
输出: [1,1,2,1,1]
解释: 通过重复调用 next 直到 hasNext 返回false,next 返回的元素的顺序应该是: [1,1,2,1,1]。

示例 2:

输入: [1,[4,[6]]]
输出: [1,4,6]
解释: 通过重复调用 next 直到 hasNext 返回false,next 返回的元素的顺序应该是: [1,4,6]。

解题思路

使用队列,将嵌套列表内的所有整数都入队,取下一个时出队。入队时,若为整数,则直接入队,若为嵌套列表,则递归调用入队函数。

代码

Python 3.6

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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.queue = []
def queue_push(n_l):
for item in n_l:
if item.isInteger():
self.queue.append(item.getInteger())
else:
queue_push(item.getList())
queue_push(nestedList)

def next(self):
"""
:rtype: int
"""
return self.queue.pop(0)

def hasNext(self):
"""
:rtype: bool
"""
return len(self.queue) > 0

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

执行用时: 92 ms
内存消耗: 17.4 MB