"content":"<p>Given the <code>root</code> of an n-ary tree, return <em>the preorder traversal of its nodes' values</em>.</p>\n\n<p>Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples)</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<p><img src=\"https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png\" style=\"width: 100%; max-width: 300px;\" /></p>\n\n<pre>\n<strong>Input:</strong> root = [1,null,3,2,4,null,5,6]\n<strong>Output:</strong> [1,3,5,6,2,4]\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<p><img alt=\"\" src=\"https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png\" style=\"width: 296px; height: 241px;\" /></p>\n\n<pre>\n<strong>Input:</strong> 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]\n<strong>Output:</strong> [1,2,3,6,7,11,14,4,8,12,5,9,13,10]\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li>The number of nodes in the tree is in the range <code>[0, 10<sup>4</sup>]</code>.</li>\n\t<li><code>0 <= Node.val <= 10<sup>4</sup></code></li>\n\t<li>The height of the n-ary tree is less than or equal to <code>1000</code>.</li>\n</ul>\n\n<p> </p>\n<p><strong>Follow up:</strong> Recursive solution is trivial, could you do it iteratively?</p>\n",
"code":"/*\n// Definition for a Node.\nclass Node {\npublic:\n int val;\n vector<Node*> children;\n\n Node() {}\n\n Node(int _val) {\n val = _val;\n }\n\n Node(int _val, vector<Node*> _children) {\n val = _val;\n children = _children;\n }\n};\n*/\n\nclass Solution {\npublic:\n vector<int> preorder(Node* root) {\n \n }\n};",
"__typename":"CodeSnippetNode"
},
{
"lang":"Java",
"langSlug":"java",
"code":"/*\n// Definition for a Node.\nclass Node {\n public int val;\n public List<Node> children;\n\n public Node() {}\n\n public Node(int _val) {\n val = _val;\n }\n\n public Node(int _val, List<Node> _children) {\n val = _val;\n children = _children;\n }\n};\n*/\n\nclass Solution {\n public List<Integer> preorder(Node root) {\n \n }\n}",
"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* preorder(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<Node> children;\n\n public Node() {}\n\n public Node(int _val) {\n val = _val;\n }\n\n public Node(int _val,IList<Node> _children) {\n val = _val;\n children = _children;\n }\n}\n*/\n\npublic class Solution {\n public IList<int> Preorder(Node root) {\n \n }\n}",
"envInfo":"{\"cpp\": [\"C++\", \"<p>Compiled with <code> clang 11 </code> using the latest C++ 20 standard.</p>\\r\\n\\r\\n<p>Your code is compiled with level two optimization (<code>-O2</code>). <a href=\\\"https://github.com/google/sanitizers/wiki/AddressSanitizer\\\" target=\\\"_blank\\\">AddressSanitizer</a> is also enabled to help detect out-of-bounds and use-after-free bugs.</p>\\r\\n\\r\\n<p>Most standard library headers are already included automatically for your convenience.</p>\"], \"java\": [\"Java\", \"<p><code>OpenJDK 17</code>. Java 8 features such as lambda expressions and stream API can be used. </p>\\r\\n\\r\\n<p>Most standard library headers are already included automatically for your convenience.</p>\\r\\n<p>Includes <code>Pair</code> class from https://docs.oracle.com/javase/8/javafx/api/javafx/util/Pair.html.</p>\"], \"python\": [\"Python\", \"<p><code>Python 2.7.12</code>.</p>\\r\\n\\r\\n<p>Most libraries are already imported automatically for your convenience, such as <a href=\\\"https://docs.python.org/2/library/array.html\\\" target=\\\"_blank\\\">array</a>, <a href=\\\"https://docs.python.org/2/library/bisect.html\\\" target=\\\"_blank\\\">bisect</a>, <a href=\\\"https://docs.python.org/2/library/collections.html\\\" target=\\\"_blank\\\">collections</a>. If you need more libraries, you can import it yourself.</p>\\r\\n\\r\\n<p>For Map/TreeMap data structure, you may use <a href=\\\"http://www.grantjenks.com/docs/sortedcontainers/\\\" target=\\\"_blank\\\">sortedcontainers</a> library.</p>\\r\\n\\r\\n<p>Note that Python 2.7 <a href=\\\"https://www.python.org/dev/peps/pep-0373/\\\" target=\\\"_blank\\\">will not be maintained past 2020</a>. For the latest Python, please choose Python3 instead.</p>\"], \"c\": [\"C\", \"<p>Compiled with <code>gcc 8.2</code> using the gnu11 standard.</p>\\r\\n\\r\\n<p>Your code is compiled with level one optimization (<code>-O1</code>). <a href=\\\"https://github.com/google/sanitizers/wiki/AddressSanitizer\\\" target=\\\"_blank\\\">AddressSanitizer</a> is also enabled to help detect out-of-bounds and use-after-free bugs.</p>\\r\\n\\r\\n<p>Most standard library headers are already included automatically for your convenience.</p>\\r\\n\\r\\n<p>For hash table operations, you may use <a href=\\\"https://troydhanson.github.io/uthash/\\\" target=\\\"_blank\\\">uthash</a>. \\\"uthash.h\\\" is included by default. Below are some examples:</p>\\r\\n\\r\\n<p><b>1. Adding an item to a hash.</b>\\r\\n<pre>\\r\\nstruct hash_entry {\\r\\n int id; /* we'll use this field as the key */\\r\\n char name[10];\\r\\n UT_hash_handle hh; /* makes this structure hashable */\\r\\n};\\r\\n\\r\\nstruct hash_entry *users = NULL;\\r\\n\\r\\nvoid add_user(struct hash_entry *s) {\\r\\n HASH_ADD_INT(users, id, s);\\r\\n}\\r\\n</pre>\\r\\n</p>\\r\\n\\r\\n<p><b>2. Looking up an item in a hash:</b>\\r\\n<pre>\\r\\nstruct hash_entry *find_user(int user_id) {\\r\\n struct hash_entry *s;\\r\\n HASH_FIND_INT(users, &user_id, s);\\r\\n return s;\\r\\n}\\r\\n</pre>\\r\\n</p>\\r\\n\\r\\n<p><b>3. Deleting an item in a hash:</b>\\r\\n<pre>\\r\\nvoid delete_user(struct hash_entry *user) {\\r\\n HASH_DEL(users, user); \\r\\n}\\r\\n</pre>\\r\\n</p>\"], \"csharp\": [\"C#\", \"<p><a href=\\\"https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-10\\\" target=\\\"_blank\\\">C# 10 with .NET 6 runtime</a></p>\"], \"javascript\": [\"JavaScript\", \"<p><code>Node.js 16.13.2</code>.</p>\\r\\n\\r\\n<p>Your code is run with <code>--harmony</code> flag, enabling <a href=\\\"http://node.green/\\\" target=\\\"_blank\\\">new ES6 features</a>.</p>\\r\\n\\r\\n<p><a href=\\\"https://lodash.com\\\" target=\\\"_blank\\\">lodash.js</a> library is included by default.</p>\\r\\n\\r\\n<p>For Priority Queue / Queue data structures, you may use 5.3.0 version of <a href=\\\"https://github.com/datastructures-js/priority-queue/tree/fb4fdb984834421279aeb081df7af624d17c2a03\\\" target=\\\"_blank\\\">datastructures-js/priority-queue</a> and 4.2.1 version of <a href=\\\"https://githu
