{ "data": { "question": { "questionId": "341", "questionFrontendId": "341", "categoryTitle": "Algorithms", "boundTopicId": 1508, "title": "Flatten Nested List Iterator", "titleSlug": "flatten-nested-list-iterator", "content": "
You are given a nested list of integers nestedList
. Each element is either an integer or a list whose elements may also be integers or other lists. Implement an iterator to flatten it.
Implement the NestedIterator
class:
NestedIterator(List<NestedInteger> nestedList)
Initializes the iterator with the nested list nestedList
.int next()
Returns the next integer in the nested list.boolean hasNext()
Returns true
if there are still some integers in the nested list and false
otherwise.Your code will be tested with the following pseudocode:
\n\n\ninitialize iterator with nestedList\nres = []\nwhile iterator.hasNext()\n append iterator.next() to the end of res\nreturn res\n\n\n
If res
matches the expected flattened list, then your code will be judged as correct.
\n
Example 1:
\n\n\nInput: nestedList = [[1,1],2,[1,1]]\nOutput: [1,1,2,1,1]\nExplanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1].\n\n\n
Example 2:
\n\n\nInput: nestedList = [1,[4,[6]]]\nOutput: [1,4,6]\nExplanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].\n\n\n
\n
Constraints:
\n\n1 <= nestedList.length <= 500
[-106, 106]
.给你一个嵌套的整数列表 nestedList
。每个元素要么是一个整数,要么是一个列表;该列表的元素也可能是整数或者是其他列表。请你实现一个迭代器将其扁平化,使之能够遍历这个列表中的所有整数。
实现扁平迭代器类 NestedIterator
:
NestedIterator(List<NestedInteger> nestedList)
用嵌套列表 nestedList
初始化迭代器。int next()
返回嵌套列表的下一个整数。boolean hasNext()
如果仍然存在待迭代的整数,返回 true
;否则,返回 false
。你的代码将会用下述伪代码检测:
\n\n\ninitialize iterator with nestedList\nres = []\nwhile iterator.hasNext()\n append iterator.next() to the end of res\nreturn res\n\n
如果 res
与预期的扁平化列表匹配,那么你的代码将会被判为正确。
\n\n
示例 1:
\n\n\n输入:nestedList = [[1,1],2,[1,1]]\n输出:[1,1,2,1,1]\n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]
。
\n\n示例 2:
\n\n\n输入:nestedList = [1,[4,[6]]]\n输出:[1,4,6]\n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]
。\n
\n\n\n\n
提示:
\n\n1 <= nestedList.length <= 500
[-106, 106]
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