{ "data": { "question": { "questionId": "776", "questionFrontendId": "590", "boundTopicId": null, "title": "N-ary Tree Postorder Traversal", "titleSlug": "n-ary-tree-postorder-traversal", "content": "

Given the root of an n-ary tree, return the postorder traversal of its nodes' values.

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Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples)

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Example 1:

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\nInput: root = [1,null,3,2,4,null,5,6]\nOutput: [5,6,3,2,4,1]\n
\n\n

Example 2:

\n\"\"\n
\nInput: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]\nOutput: [2,6,14,11,7,3,12,8,4,13,9,10,5,1]\n
\n\n

 

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Constraints:

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Follow up: Recursive solution is trivial, could you do it iteratively?

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"langSlug": "python", "code": "\"\"\"\n# Definition for a Node.\nclass Node(object):\n def __init__(self, val=None, children=None):\n self.val = val\n self.children = children\n\"\"\"\n\nclass Solution(object):\n def postorder(self, root):\n \"\"\"\n :type root: Node\n :rtype: List[int]\n \"\"\"\n ", "__typename": "CodeSnippetNode" }, { "lang": "Python3", "langSlug": "python3", "code": "\"\"\"\n# Definition for a Node.\nclass Node:\n def __init__(self, val=None, children=None):\n self.val = val\n self.children = children\n\"\"\"\n\nclass Solution:\n def postorder(self, root: 'Node') -> List[int]:\n ", "__typename": "CodeSnippetNode" }, { "lang": "C", "langSlug": "c", "code": "/**\n * Definition for a Node.\n * struct Node {\n * int val;\n * int numChildren;\n * struct Node** children;\n * };\n */\n\n/**\n * Note: The returned array must be malloced, assume caller calls free().\n */\nint* postorder(struct Node* root, int* returnSize) {\n \n}", "__typename": "CodeSnippetNode" }, { "lang": "C#", "langSlug": "csharp", "code": "/*\n// Definition for a Node.\npublic class Node {\n public int val;\n public IList children;\n\n public Node() {}\n\n public Node(int _val) {\n val = _val;\n }\n\n public Node(int _val, IList _children) {\n val = _val;\n children = _children;\n }\n}\n*/\n\npublic class Solution {\n public IList Postorder(Node root) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "JavaScript", "langSlug": "javascript", "code": "/**\n * // Definition for a Node.\n * function Node(val,children) {\n * this.val = val;\n * this.children = children;\n * };\n */\n\n/**\n * @param {Node|null} root\n * @return {number[]}\n */\nvar postorder = function(root) {\n \n};", "__typename": "CodeSnippetNode" }, { "lang": "Ruby", "langSlug": "ruby", "code": "# Definition for a Node.\n# class Node\n# attr_accessor :val, :children\n# def initialize(val)\n# @val = val\n# @children = []\n# end\n# end\n\n# @param {Node} root\n# @return {List[int]}\ndef postorder(root)\n \nend", "__typename": "CodeSnippetNode" }, { "lang": "Swift", "langSlug": "swift", "code": "/**\n * Definition for a Node.\n * public class Node {\n * public var val: Int\n * public var children: [Node]\n * public init(_ val: Int) {\n * self.val = val\n * self.children = []\n * }\n * }\n */\n\nclass Solution {\n func postorder(_ root: Node?) -> [Int] {\n \t\n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Go", "langSlug": "golang", "code": "/**\n * Definition for a Node.\n * type Node struct {\n * Val int\n * Children []*Node\n * }\n */\n\nfunc postorder(root *Node) []int {\n \n}", "__typename": "CodeSnippetNode" }, { "lang": "Scala", "langSlug": "scala", "code": "/**\n * Definition for a Node.\n * class Node(var _value: Int) {\n * var value: Int = _value\n * var children: List[Node] = List()\n * }\n */\n\nobject Solution {\n def postorder(root: Node): List[Int] = {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Kotlin", "langSlug": "kotlin", "code": "/**\n * Definition for a Node.\n * class Node(var `val`: Int) {\n * var children: List = listOf()\n * }\n */\n\nclass Solution {\n fun postorder(root: Node?): List {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "PHP", "langSlug": "php", "code": "/**\n * Definition for a Node.\n * class Node {\n * public $val = null;\n * public $children = null;\n * function __construct($val = 0) {\n * $this->val = $val;\n * $this->children = array();\n * }\n * }\n */\n\nclass Solution {\n /**\n * @param Node $root\n * @return integer[]\n */\n function postorder($root) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "TypeScript", "langSlug": "typescript", "code": "/**\n * Definition for node.\n * class Node {\n * val: number\n * children: Node[]\n * constructor(val?: number) {\n * this.val = (val===undefined ? 0 : val)\n * this.children = []\n * }\n * }\n */\n\nfunction postorder(root: Node | null): number[] {\n\n};", "__typename": "CodeSnippetNode" } ], "stats": "{\"totalAccepted\": 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Compiled with clang 11 using the latest C++ 17 standard.

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Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.

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Most standard library headers are already included automatically for your convenience.

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OpenJDK 17 . Java 8 features such as lambda expressions and stream API can be used.

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Most standard library headers are already included automatically for your convenience.

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Includes Pair class from https://docs.oracle.com/javase/8/javafx/api/javafx/util/Pair.html.

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Python 2.7.12.

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Most libraries are already imported automatically for your convenience, such as array, bisect, collections. If you need more libraries, you can import it yourself.

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Compiled with gcc 8.2 using the gnu99 standard.

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C# 10 with .NET 6 runtime

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Your code is compiled with debug flag enabled (/debug).

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Node.js 16.13.2.

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Your code is run with --harmony flag, enabling new ES6 features.

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lodash.js library is included by default.

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For Priority Queue / Queue data structures, you may use datastructures-js/priority-queue and datastructures-js/queue.

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Ruby 3.1

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Some common data structure implementations are provided in the Algorithms module: https://www.rubydoc.info/github/kanwei/algorithms/Algorithms

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