"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 class=\"example\">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() {\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 */",
"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.",
"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++ 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