"content":"<p>Implement the <code>BSTIterator</code> class that represents an iterator over the <strong><a href=\"https://en.wikipedia.org/wiki/Tree_traversal#In-order_(LNR)\" target=\"_blank\">in-order traversal</a></strong> of a binary search tree (BST):</p>\n\n<ul>\n\t<li><code>BSTIterator(TreeNode root)</code> Initializes an object of the <code>BSTIterator</code> class. The <code>root</code> of the BST is given as part of the constructor. The pointer should be initialized to a non-existent number smaller than any element in the BST.</li>\n\t<li><code>boolean hasNext()</code> Returns <code>true</code> if there exists a number in the traversal to the right of the pointer, otherwise returns <code>false</code>.</li>\n\t<li><code>int next()</code> Moves the pointer to the right, then returns the number at the pointer.</li>\n</ul>\n\n<p>Notice that by initializing the pointer to a non-existent smallest number, the first call to <code>next()</code> will return the smallest element in the BST.</p>\n\n<p>You may assume that <code>next()</code> calls will always be valid. That is, there will be at least a next number in the in-order traversal when <code>next()</code> is called.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2018/12/25/bst-tree.png\" style=\"width: 189px; height: 178px;\" />\n<pre>\n<strong>Input</strong>\n["BSTIterator", "next", "next", "hasNext", "next", "hasNext", "next", "hasNext", "next", "hasNext"]\n[[[7, 3, 15, null, null, 9, 20]], [], [], [], [], [], [], [], [], []]\n<strong>Output</strong>\n[null, 3, 7, true, 9, true, 15, true, 20, false]\n\n<strong>Explanation</strong>\nBSTIterator bSTIterator = new BSTIterator([7, 3, 15, null, null, 9, 20]);\nbSTIterator.next(); // return 3\nbSTIterator.next(); // return 7\nbSTIterator.hasNext(); // return True\nbSTIterator.next(); // return 9\nbSTIterator.hasNext(); // return True\nbSTIterator.next(); // return 15\nbSTIterator.hasNext(); // return True\nbSTIterator.next(); // return 20\nbSTIterator.hasNext(); // return False\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>[1, 10<sup>5</sup>]</code>.</li>\n\t<li><code>0 <= Node.val <= 10<sup>6</sup></code></li>\n\t<li>At most <code>10<sup>5</sup></code> calls will be made to <code>hasNext</code>, and <code>next</code>.</li>\n</ul>\n\n<p> </p>\n<p><strong>Follow up:</strong></p>\n\n<ul>\n\t<li>Could you implement <code>next()</code> and <code>hasNext()</code> to run in average <code>O(1)</code> time and use <code>O(h)</code> memory, where <code>h</code> is the height of the tree?</li>\n</ul>\n",
"code":"/**\n * Definition for a binary tree node.\n * public class TreeNode {\n * public int val;\n * public TreeNode left;\n * public TreeNode right;\n * public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {\n * this.val = val;\n * this.left = left;\n * this.right = right;\n * }\n * }\n */\npublic class BSTIterator {\n\n public BSTIterator(TreeNode root) {\n \n }\n \n public int Next() {\n \n }\n \n public bool HasNext() {\n \n }\n}\n\n/**\n * Your BSTIterator object will be instantiated and called as such:\n * BSTIterator obj = new BSTIterator(root);\n * int param_1 = obj.Next();\n * bool param_2 = obj.HasNext();\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"JavaScript",
"langSlug":"javascript",
"code":"/**\n * Definition for a binary tree node.\n * function TreeNode(val, left, right) {\n * this.val = (val===undefined ? 0 : val)\n * this.left = (left===undefined ? null : left)\n * this.right = (right===undefined ? null : right)\n * }\n */\n/**\n * @param {TreeNode} root\n */\nvar BSTIterator = function(root) {\n \n};\n\n/**\n * @return {number}\n */\nBSTIterator.prototype.next = function() {\n \n};\n\n/**\n * @return {boolean}\n */\nBSTIterator.prototype.hasNext = function() {\n \n};\n\n/** \n * Your BSTIterator object will be instantiated and called as such:\n * var obj = new BSTIterator(root)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
"code":"/**\n * Example:\n * var ti = TreeNode(5)\n * var v = ti.`val`\n * Definition for a binary tree node.\n * class TreeNode(var `val`: Int) {\n * var left: TreeNode? = null\n * var right: TreeNode? = null\n * }\n */\nclass BSTIterator(root: TreeNode?) {\n\n fun next(): Int {\n \n }\n\n fun hasNext(): Boolean {\n \n }\n\n}\n\n/**\n * Your BSTIterator object will be instantiated and called as such:\n * var obj = BSTIterator(root)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
"code":"/**\n * Definition for a binary tree node.\n * type TreeNode struct {\n * Val int\n * Left *TreeNode\n * Right *TreeNode\n * }\n */\ntype BSTIterator struct {\n \n}\n\n\nfunc Constructor(root *TreeNode) BSTIterator {\n \n}\n\n\nfunc (this *BSTIterator) Next() int {\n \n}\n\n\nfunc (this *BSTIterator) HasNext() bool {\n \n}\n\n\n/**\n * Your BSTIterator object will be instantiated and called as such:\n * obj := Constructor(root);\n * param_1 := obj.Next();\n * param_2 := obj.HasNext();\n */",
"code":"/**\n * Definition for a binary tree node.\n * class TreeNode(_value: Int = 0, _left: TreeNode = null, _right: TreeNode = null) {\n * var value: Int = _value\n * var left: TreeNode = _left\n * var right: TreeNode = _right\n * }\n */\nclass BSTIterator(_root: TreeNode) {\n\n def next(): Int = {\n \n }\n\n def hasNext(): Boolean = {\n \n }\n\n}\n\n/**\n * Your BSTIterator object will be instantiated and called as such:\n * var obj = new BSTIterator(root)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
"code":"%% Definition for a binary tree node.\n%%\n%% -record(tree_node, {val = 0 :: integer(),\n%% left = null :: 'null' | #tree_node{},\n%% right = null :: 'null' | #tree_node{}}).\n\n-spec bst_iterator_init_(Root :: #tree_node{} | null) -> any().\nbst_iterator_init_(Root) ->\n .\n\n-spec bst_iterator_next() -> integer().\nbst_iterator_next() ->\n .\n\n-spec bst_iterator_has_next() -> boolean().\nbst_iterator_has_next() ->\n .\n\n\n%% Your functions will be called as such:\n%% bst_iterator_init_(Root),\n%% Param_1 = bst_iterator_next(),\n%% Param_2 = bst_iterator_has_next(),\n\n%% bst_iterator_init_ will be called before every test case, in which you can do some necessary initializations.",
"code":"# Definition for a binary tree node.\n#\n# defmodule TreeNode do\n# @type t :: %__MODULE__{\n# val: integer,\n# left: TreeNode.t() | nil,\n# right: TreeNode.t() | nil\n# }\n# defstruct val: 0, left: nil, right: nil\n# end\n\ndefmodule BSTIterator do\n @spec init_(root :: TreeNode.t | nil) :: any\n def init_(root) do\n \n end\n\n @spec next() :: integer\n def next() do\n \n end\n\n @spec has_next() :: boolean\n def has_next() do\n \n end\nend\n\n# Your functions will be called as such:\n# BSTIterator.init_(root)\n# param_1 = BSTIterator.next()\n# param_2 = BSTIterator.has_next()\n\n# BSTIterator.init_ will be called before every test case, in which you can do some necessary initializations.",
"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
