Populating Next Right Pointers in Each Node II
<p>Given a binary tree</p>

<pre>
struct Node {
  int val;
  Node *left;
  Node *right;
  Node *next;
}
</pre>

<p>Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to <code>NULL</code>.</p>

<p>Initially, all next pointers are set to <code>NULL</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/02/15/117_sample.png" style="width: 500px; height: 171px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,4,5,null,7]
<strong>Output:</strong> [1,#,2,3,#,4,5,7,#]
<strong>Explanation: </strong>Given the above binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B. The serialized output is in level order as connected by the next pointers, with &#39;#&#39; signifying the end of each level.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> root = []
<strong>Output:</strong> []
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[0, 6000]</code>.</li>
	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Follow-up:</strong></p>

<ul>
	<li>You may only use constant extra space.</li>
	<li>The recursive approach is fine. You may assume implicit stack space does not count as extra space for this problem.</li>
</ul>

['populating-next-right-pointers-in-each-node']
[]
[{"value": "cpp", "text": "C++", "defaultCode": "/*\n// Definition for a Node.\nclass Node {\npublic:\n    int val;\n    Node* left;\n    Node* right;\n    Node* next;\n\n    Node() : val(0), left(NULL), right(NULL), next(NULL) {}\n\n    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}\n\n    Node(int _val, Node* _left, Node* _right, Node* _next)\n        : val(_val), left(_left), right(_right), next(_next) {}\n};\n*/\n\nclass Solution {\npublic:\n    Node* connect(Node* root) {\n        \n    }\n};"}, {"value": "java", "text": "Java", "defaultCode": "/*\n// Definition for a Node.\nclass Node {\n    public int val;\n    public Node left;\n    public Node right;\n    public Node next;\n\n    public Node() {}\n    \n    public Node(int _val) {\n        val = _val;\n    }\n\n    public Node(int _val, Node _left, Node _right, Node _next) {\n        val = _val;\n        left = _left;\n        right = _right;\n        next = _next;\n    }\n};\n*/\n\nclass Solution {\n    public Node connect(Node root) {\n        \n    }\n}"}, {"value": "python", "text": "Python", "defaultCode": "\"\"\"\n# Definition for a Node.\nclass Node(object):\n    def __init__(self, val=0, left=None, right=None, next=None):\n        self.val = val\n        self.left = left\n        self.right = right\n        self.next = next\n\"\"\"\n\nclass Solution(object):\n    def connect(self, root):\n        \"\"\"\n        :type root: Node\n        :rtype: Node\n        \"\"\"\n        "}, {"value": "python3", "text": "Python3", "defaultCode": "\"\"\"\n# Definition for a Node.\nclass Node:\n    def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):\n        self.val = val\n        self.left = left\n        self.right = right\n        self.next = next\n\"\"\"\n\nclass Solution:\n    def connect(self, root: 'Node') -> 'Node':\n        "}, {"value": "c", "text": "C", "defaultCode": "/**\n * Definition for a Node.\n * struct Node {\n *     int val;\n *     struct Node *left;\n *     struct Node *right;\n *     struct Node *next;\n * };\n */\n\nstruct Node* connect(struct Node* root) {\n\t\n}"}, {"value": "csharp", "text": "C#", "defaultCode": "/*\n// Definition for a Node.\npublic class Node {\n    public int val;\n    public Node left;\n    public Node right;\n    public Node next;\n\n    public Node() {}\n\n    public Node(int _val) {\n        val = _val;\n    }\n\n    public Node(int _val, Node _left, Node _right, Node _next) {\n        val = _val;\n        left = _left;\n        right = _right;\n        next = _next;\n    }\n}\n*/\n\npublic class Solution {\n    public Node Connect(Node root) {\n        \n    }\n}"}, {"value": "javascript", "text": "JavaScript", "defaultCode": "/**\n * // Definition for a _Node.\n * function _Node(val, left, right, next) {\n *    this.val = val === undefined ? null : val;\n *    this.left = left === undefined ? null : left;\n *    this.right = right === undefined ? null : right;\n *    this.next = next === undefined ? null : next;\n * };\n */\n\n/**\n * @param {_Node} root\n * @return {_Node}\n */\nvar connect = function(root) {\n    \n};"}, {"value": "typescript", "text": "TypeScript", "defaultCode": "/**\n * Definition for _Node.\n * class _Node {\n *     val: number\n *     left: _Node | null\n *     right: _Node | null\n *     next: _Node | null\n * \n *     constructor(val?: number, left?: _Node, right?: _Node, next?: _Node) {\n *         this.val = (val===undefined ? 0 : val)\n *         this.left = (left===undefined ? null : left)\n *         this.right = (right===undefined ? null : right)\n *         this.next = (next===undefined ? null : next)\n *     }\n * }\n */\n\n\nfunction connect(root: _Node | null): _Node | null {\n    \n};"}, {"value": "php", "text": "PHP", "defaultCode": "/**\n * Definition for a Node.\n * class Node {\n *     function __construct($val = 0) {\n *         $this->val = $val;\n *         $this->left = null;\n *         $this->right = null;\n *         $this->next = null;\n *     }\n * }\n */\n\nclass Solution {\n    /**\n     * @param Node $root\n     * @return Node\n     */\n    public function connect($root) {\n        \n    }\n}"}, {"value": "swift", "text": "Swift", "defaultCode": "/**\n * Definition for a Node.\n * public class Node {\n *     public var val: Int\n *     public var left: Node?\n *     public var right: Node?\n *\t   public var next: Node?\n *     public init(_ val: Int) {\n *         self.val = val\n *         self.left = nil\n *         self.right = nil\n *         self.next = nil\n *     }\n * }\n */\n\nclass Solution {\n    func connect(_ root: Node?) -> Node? {\n        \n    }\n}"}, {"value": "kotlin", "text": "Kotlin", "defaultCode": "/**\n * Definition for a Node.\n * class Node(var `val`: Int) {\n *     var left: Node? = null\n *     var right: Node? = null\n *     var next: Node? = null\n * }\n */\n\nclass Solution {\n    fun connect(root: Node?): Node? {\n        \n    }\n}"}, {"value": "golang", "text": "Go", "defaultCode": "/**\n * Definition for a Node.\n * type Node struct {\n *     Val int\n *     Left *Node\n *     Right *Node\n *     Next *Node\n * }\n */\n\nfunc connect(root *Node) *Node {\n\t\n}"}, {"value": "ruby", "text": "Ruby", "defaultCode": "# Definition for a Node.\n# class Node\n#     attr_accessor :val, :left, :right, :next\n#     def initialize(val)\n#         @val = val\n#         @left, @right, @next = nil, nil, nil\n#     end\n# end\n\n# @param {Node} root\n# @return {Node}\ndef connect(root)\n    \nend"}, {"value": "scala", "text": "Scala", "defaultCode": "/**\n * Definition for a Node.\n * class Node(var _value: Int) {\n *   var value: Int = _value\n *   var left: Node = null\n *   var right: Node = null\n *   var next: Node = null\n * }\n */\n\nobject Solution {\n    def connect(root: Node): Node = {\n        \n    }\n}"}]
{
  "name": "connect",
  "params": [
    {
      "name": "root",
      "type": "TreeNode"
    }
  ],
  "return": {
    "type": "TreeNode"
  },
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  "manual": true,
      "typescriptCustomType" : "class _Node {\n    val: number\n    left: _Node | null\n    right: _Node | null\n    next: _Node | null\n\n    constructor(val?: number, left?: _Node, right?: _Node, next?: _Node) {\n        this.val = (val===undefined ? 0 : val)\n        this.left = (left===undefined ? null : left)\n        this.right = (right===undefined ? null : right)\n        this.next = (next===undefined ? null : next)\n    }\n}\n"

}
{"cpp": ["C++", "<p>Compiled with <code> clang 19 </code> using the latest C++ 23 standard, and <code>libstdc++</code> provided by GCC 14.</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 21</code>. Using compile arguments: <code>--enable-preview --release 21</code></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 2.7.18</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\">is not maintained anymore</a>. For the latest Python, please choose Python3 instead.</p>"], "c": ["C", "<p>Compiled with <code>gcc 14</code> using the gnu11 standard.</p>\r\n\r\n<p>Your code is compiled with level one 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>\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-13\" target=\"_blank\">C# 13</a> with .NET 9 runtime</p>"], "javascript": ["JavaScript", "<p><code>Node.js 22.14.0</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 6.3.2 version of <a href=\"https://github.com/datastructures-js/priority-queue/tree/v6.3.2\" target=\"_blank\">datastructures-js/priority-queue</a> and 4.2.3 version of <a href=\"https://github.com/datastructures-js/queue/tree/v4.2.3\" target=\"_blank\">datastructures-js/queue</a> and 1.0.4 version of <a href=\"https://github.com/datastructures-js/deque/tree/v1.0.4\" target=\"_blank\">datastructures-js/deque</a>.</p>"], "ruby": ["Ruby", "<p><code>Ruby 3.2</code></p>\r\n\r\n<p>Some common data structure implementations are provided in the Algorithms module: https://www.rubydoc.info/github/kanwei/algorithms/Algorithms</p>"], "swift": ["Swift", "<p><code>Swift 6.0</code>.</p>\r\n\r\n<p>You may use the following packages:<br/>\r\n<a href=\"https://github.com/apple/swift-algorithms/tree/1.2.0\" target=\"_blank\">swift-algorithms 1.2.0</a><br/>\r\n<a href=\"https://github.com/apple/swift-collections/tree/1.1.4\" target=\"_blank\">swift-collections 1.1.4</a><br/>\r\n<a href=\"https://github.com/apple/swift-numerics/tree/1.0.2\" target=\"_blank\">swift-numerics 1.0.2</a></p>"], "golang": ["Go", "<p><code>Go 1.23</code></p>\r\n<p>Support <a href=\"https://pkg.go.dev/github.com/emirpasic/gods@v1.18.1\" target=\"_blank\">https://pkg.go.dev/github.com/emirpasic/gods@v1.18.1</a> and <a href=\"https://pkg.go.dev/github.com/emirpasic/gods/v2@v2.0.0-alpha\" target=\"_blank\">https://pkg.go.dev/github.com/emirpasic/gods/v2@v2.0.0-alpha</a> library.</p>"], "python3": ["Python3", "<p><code>Python 3.11</code>.</p>\r\n\r\n<p>Most libraries are already imported automatically for your convenience, such as <a href=\"https://docs.python.org/3/library/array.html\" target=\"_blank\">array</a>, <a href=\"https://docs.python.org/3/library/bisect.html\" target=\"_blank\">bisect</a>, <a href=\"https://docs.python.org/3/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>"], "scala": ["Scala", "<p><code>Scala 3.3.1</code>.</p>"], "kotlin": ["Kotlin", "<p><code>Kotlin 2.1.10</code>.</p>"], "php": ["PHP", "<p><code>PHP 8.2</code>.</p>\r\n<p>With bcmath module</p>"], "typescript": ["Typescript", "<p><code>TypeScript 5.7.3, Node.js 22.14.0</code>.</p>\r\n\r\n<p>Compile Options: <code>--alwaysStrict --strictBindCallApply --strictFunctionTypes --target ES2024</code></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 6.3.2 version of <a href=\"https://github.com/datastructures-js/priority-queue/tree/v6.3.2\" target=\"_blank\">datastructures-js/priority-queue</a> and 4.2.3 version of <a href=\"https://github.com/datastructures-js/queue/tree/v4.2.3\" target=\"_blank\">datastructures-js/queue</a> and 1.0.4 version of <a href=\"https://github.com/datastructures-js/deque/tree/v1.0.4\" target=\"_blank\">datastructures-js/deque</a>.</p>"]}
['Linked List', 'Tree', 'Depth-First Search', 'Breadth-First Search', 'Binary Tree']