"content":"<p>Design a <strong>Skiplist</strong> without using any built-in libraries.</p>\n\n<p>A <strong>skiplist</strong> is a data structure that takes <code>O(log(n))</code> time to add, erase and search. Comparing with treap and red-black tree which has the same function and performance, the code length of Skiplist can be comparatively short and the idea behind Skiplists is just simple linked lists.</p>\n\n<p>For example, we have a Skiplist containing <code>[30,40,50,60,70,90]</code> and we want to add <code>80</code> and <code>45</code> into it. The Skiplist works this way:</p>\n\n<p><img alt=\"\" src=\"https://assets.leetcode.com/uploads/2019/09/27/1506_skiplist.gif\" style=\"width: 500px; height: 173px;\" /><br />\n<small>Artyom Kalinin [CC BY-SA 3.0], via <a href=\"https://commons.wikimedia.org/wiki/File:Skip_list_add_element-en.gif\" target=\"_blank\" title=\"Artyom Kalinin [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons\">Wikimedia Commons</a></small></p>\n\n<p>You can see there are many layers in the Skiplist. Each layer is a sorted linked list. With the help of the top layers, add, erase and search can be faster than <code>O(n)</code>. It can be proven that the average time complexity for each operation is <code>O(log(n))</code> and space complexity is <code>O(n)</code>.</p>\n\n<p>See more about Skiplist: <a href=\"https://en.wikipedia.org/wiki/Skip_list\" target=\"_blank\">https://en.wikipedia.org/wiki/Skip_list</a></p>\n\n<p>Implement the <code>Skiplist</code> class:</p>\n\n<ul>\n\t<li><code>Skiplist()</code> Initializes the object of the skiplist.</li>\n\t<li><code>bool search(int target)</code> Returns <code>true</code> if the integer <code>target</code> exists in the Skiplist or <code>false</code> otherwise.</li>\n\t<li><code>void add(int num)</code> Inserts the value <code>num</code> into the SkipList.</li>\n\t<li><code>bool erase(int num)</code> Removes the value <code>num</code> from the Skiplist and returns <code>true</code>. If <code>num</code> does not exist in the Skiplist, do nothing and return <code>false</code>. If there exist multiple <code>num</code> values, removing any one of them is fine.</li>\n</ul>\n\n<p>Note that duplicates may exist in the Skiplist, your code needs to handle this situation.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input</strong>\n["Skiplist", "add", "add", "add", "search", "add", "search", "erase", "erase", "search"]\n[[], [1], [2], [3], [0], [4], [1], [0], [1], [1]]\n<strong>Output</strong>\n[null, null, null, null, false, null, true, false, true, false]\n\n<strong>Explanation</strong>\nSkiplist skiplist = new Skiplist();\nskiplist.add(1);\nskiplist.add(2);\nskiplist.add(3);\nskiplist.search(0); // return False\nskiplist.add(4);\nskiplist.search(1); // return True\nskiplist.erase(0); // return False, 0 is not in skiplist.\nskiplist.erase(1); // return True\nskiplist.search(1); // return False, 1 has already been erased.</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= num, target <= 2 * 10<sup>4</sup></code></li>\n\t<li>At most <code>5 * 10<sup>4</sup></code> calls will be made to <code>search</code>, <code>add</code>, and <code>erase</code>.</li>\n</ul>\n",
"code":"class Skiplist {\npublic:\n Skiplist() {\n \n }\n \n bool search(int target) {\n \n }\n \n void add(int num) {\n \n }\n \n bool erase(int num) {\n \n }\n};\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * Skiplist* obj = new Skiplist();\n * bool param_1 = obj->search(target);\n * obj->add(num);\n * bool param_3 = obj->erase(num);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Java",
"langSlug":"java",
"code":"class Skiplist {\n\n public Skiplist() {\n \n }\n \n public boolean search(int target) {\n \n }\n \n public void add(int num) {\n \n }\n \n public boolean erase(int num) {\n \n }\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * Skiplist obj = new Skiplist();\n * boolean param_1 = obj.search(target);\n * obj.add(num);\n * boolean param_3 = obj.erase(num);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Python",
"langSlug":"python",
"code":"class Skiplist(object):\n\n def __init__(self):\n \n\n def search(self, target):\n \"\"\"\n :type target: int\n :rtype: bool\n \"\"\"\n \n\n def add(self, num):\n \"\"\"\n :type num: int\n :rtype: None\n \"\"\"\n \n\n def erase(self, num):\n \"\"\"\n :type num: int\n :rtype: bool\n \"\"\"\n \n\n\n# Your Skiplist object will be instantiated and called as such:\n# obj = Skiplist()\n# param_1 = obj.search(target)\n# obj.add(num)\n# param_3 = obj.erase(num)",
"__typename":"CodeSnippetNode"
},
{
"lang":"Python3",
"langSlug":"python3",
"code":"class Skiplist:\n\n def __init__(self):\n \n\n def search(self, target: int) -> bool:\n \n\n def add(self, num: int) -> None:\n \n\n def erase(self, num: int) -> bool:\n \n\n\n# Your Skiplist object will be instantiated and called as such:\n# obj = Skiplist()\n# param_1 = obj.search(target)\n# obj.add(num)\n# param_3 = obj.erase(num)",
"__typename":"CodeSnippetNode"
},
{
"lang":"C",
"langSlug":"c",
"code":"\n\n\ntypedef struct {\n \n} Skiplist;\n\n\nSkiplist* skiplistCreate() {\n \n}\n\nbool skiplistSearch(Skiplist* obj, int target) {\n \n}\n\nvoid skiplistAdd(Skiplist* obj, int num) {\n \n}\n\nbool skiplistErase(Skiplist* obj, int num) {\n \n}\n\nvoid skiplistFree(Skiplist* obj) {\n \n}\n\n/**\n * Your Skiplist struct will be instantiated and called as such:\n * Skiplist* obj = skiplistCreate();\n * bool param_1 = skiplistSearch(obj, target);\n \n * skiplistAdd(obj, num);\n \n * bool param_3 = skiplistErase(obj, num);\n \n * skiplistFree(obj);\n*/",
"__typename":"CodeSnippetNode"
},
{
"lang":"C#",
"langSlug":"csharp",
"code":"public class Skiplist {\n\n public Skiplist() {\n \n }\n \n public bool Search(int target) {\n \n }\n \n public void Add(int num) {\n \n }\n \n public bool Erase(int num) {\n \n }\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * Skiplist obj = new Skiplist();\n * bool param_1 = obj.Search(target);\n * obj.Add(num);\n * bool param_3 = obj.Erase(num);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"JavaScript",
"langSlug":"javascript",
"code":"\nvar Skiplist = function() {\n \n};\n\n/** \n * @param {number} target\n * @return {boolean}\n */\nSkiplist.prototype.search = function(target) {\n \n};\n\n/** \n * @param {number} num\n * @return {void}\n */\nSkiplist.prototype.add = function(num) {\n \n};\n\n/** \n * @param {number} num\n * @return {boolean}\n */\nSkiplist.prototype.erase = function(num) {\n \n};\n\n/** \n * Your Skiplist object will be instantiated and called as such:\n * var obj = new Skiplist()\n * var param_1 = obj.search(target)\n * obj.add(num)\n * var param_3 = obj.erase(num)\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Ruby",
"langSlug":"ruby",
"code":"class Skiplist\n def initialize()\n \n end\n\n\n=begin\n :type target: Integer\n :rtype: Boolean\n=end\n def search(target)\n \n end\n\n\n=begin\n :type num: Integer\n :rtype: Void\n=end\n def add(num)\n \n end\n\n\n=begin\n :type num: Integer\n :rtype: Boolean\n=end\n def erase(num)\n \n end\n\n\nend\n\n# Your Skiplist object will be instantiated and called as such:\n# obj = Skiplist.new()\n# param_1 = obj.search(target)\n# obj.add(num)\n# param_3 = obj.erase(num)",
"__typename":"CodeSnippetNode"
},
{
"lang":"Swift",
"langSlug":"swift",
"code":"\nclass Skiplist {\n\n init() {\n \n }\n \n func search(_ target: Int) -> Bool {\n \n }\n \n func add(_ num: Int) {\n \n }\n \n func erase(_ num: Int) -> Bool {\n \n }\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * let obj = Skiplist()\n * let ret_1: Bool = obj.search(target)\n * obj.add(num)\n * let ret_3: Bool = obj.erase(num)\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Go",
"langSlug":"golang",
"code":"type Skiplist struct {\n \n}\n\n\nfunc Constructor() Skiplist {\n \n}\n\n\nfunc (this *Skiplist) Search(target int) bool {\n \n}\n\n\nfunc (this *Skiplist) Add(num int) {\n \n}\n\n\nfunc (this *Skiplist) Erase(num int) bool {\n \n}\n\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * obj := Constructor();\n * param_1 := obj.Search(target);\n * obj.Add(num);\n * param_3 := obj.Erase(num);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Scala",
"langSlug":"scala",
"code":"class Skiplist() {\n\n def search(target: Int): Boolean = {\n \n }\n\n def add(num: Int) {\n \n }\n\n def erase(num: Int): Boolean = {\n \n }\n\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * var obj = new Skiplist()\n * var param_1 = obj.search(target)\n * obj.add(num)\n * var param_3 = obj.erase(num)\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Kotlin",
"langSlug":"kotlin",
"code":"class Skiplist() {\n\n fun search(target: Int): Boolean {\n \n }\n\n fun add(num: Int) {\n \n }\n\n fun erase(num: Int): Boolean {\n \n }\n\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * var obj = Skiplist()\n * var param_1 = obj.search(target)\n * obj.add(num)\n * var param_3 = obj.erase(num)\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Rust",
"langSlug":"rust",
"code":"struct Skiplist {\n\n}\n\n\n/** \n * `&self` means the method takes an immutable reference.\n * If you need a mutable reference, change it to `&mut self` instead.\n */\nimpl Skiplist {\n\n fn new() -> Self {\n \n }\n \n fn search(&self, target: i32) -> bool {\n \n }\n \n fn add(&self, num: i32) {\n \n }\n \n fn erase(&self, num: i32) -> bool {\n \n }\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * let obj = Skiplist::new();\n * let ret_1: bool = obj.search(target);\n * obj.add(num);\n * let ret_3: bool = obj.erase(num);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"PHP",
"langSlug":"php",
"code":"class Skiplist {\n /**\n */\n function __construct() {\n \n }\n \n /**\n * @param Integer $target\n * @return Boolean\n */\n function search($target) {\n \n }\n \n /**\n * @param Integer $num\n * @return NULL\n */\n function add($num) {\n \n }\n \n /**\n * @param Integer $num\n * @return Boolean\n */\n function erase($num) {\n \n }\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * $obj = Skiplist();\n * $ret_1 = $obj->search($target);\n * $obj->add($num);\n * $ret_3 = $obj->erase($num);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"TypeScript",
"langSlug":"typescript",
"code":"class Skiplist {\n constructor() {\n\n }\n\n search(target: number): boolean {\n\n }\n\n add(num: number): void {\n\n }\n\n erase(num: number): boolean {\n\n }\n}\n\n/**\n * Your Skiplist object will be instantiated and called as such:\n * var obj = new Skiplist()\n * var param_1 = obj.search(target)\n * obj.add(num)\n * var param_3 = obj.erase(num)\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Racket",
"langSlug":"racket",
"code":"(define skiplist%\n (class object%\n (super-new)\n (init-field)\n \n ; search : exact-integer? -> boolean?\n (define/public (search target)\n\n )\n ; add : exact-integer? -> void?\n (define/public (add num)\n\n )\n ; erase : exact-integer? -> boolean?\n (define/public (erase num)\n\n )))\n\n;; Your skiplist% object will be instantiated and called as such:\n;; (define obj (new skiplist%))\n;; (define param_1 (send obj search target))\n;; (send obj add num)\n;; (define param_3 (send obj erase num))",
"__typename":"CodeSnippetNode"
},
{
"lang":"Erlang",
"langSlug":"erlang",
"code":"-spec skiplist_init_() -> any().\nskiplist_init_() ->\n .\n\n-spec skiplist_search(Target :: integer()) -> boolean().\nskiplist_search(Target) ->\n .\n\n-spec skiplist_add(Num :: integer()) -> any().\nskiplist_add(Num) ->\n .\n\n-spec skiplist_erase(Num :: integer()) -> boolean().\nskiplist_erase(Num) ->\n .\n\n\n%% Your functions will be called as such:\n%% skiplist_init_(),\n%% Param_1 = skiplist_search(Target),\n%% skiplist_add(Num),\n%% Param_3 = skiplist_erase(Num),\n\n%% skiplist_init_ will be called before every test case, in which you can do some necessary initializations.",
"__typename":"CodeSnippetNode"
},
{
"lang":"Elixir",
"langSlug":"elixir",
"code":"defmodule Skiplist do\n @spec init_() :: any\n def init_() do\n\n end\n\n @spec search(target :: integer) :: boolean\n def search(target) do\n\n end\n\n @spec add(num :: integer) :: any\n def add(num) do\n\n end\n\n @spec erase(num :: integer) :: boolean\n def erase(num) do\n\n end\nend\n\n# Your functions will be called as such:\n# Skiplist.init_()\n# param_1 = Skiplist.search(target)\n# Skiplist.add(num)\n# param_3 = Skiplist.erase(num)\n\n# Skiplist.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++ 17 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 gnu99 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://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-9\\\" target=\\\"_blank\\\">C# 10 with .NET 6 runtime</a></p>\\r\\n\\r\\n<p>Your code is compiled with debug flag enabled (<code>/debug</code>).</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 <a href=\\\"https://github.com/datastructures-js/priority-queue\\\" target=\\\"_blank\\\">datastructures-js/priority-queue</a> and <a href=\\\"https:
