{
    "data": {
        "question": {
            "questionId": "894",
            "questionFrontendId": "710",
            "boundTopicId": null,
            "title": "Random Pick with Blacklist",
            "titleSlug": "random-pick-with-blacklist",
            "content": "<p>You are given an integer <code>n</code> and an array of <strong>unique</strong> integers <code>blacklist</code>. Design an algorithm to pick a random integer in the range <code>[0, n - 1]</code> that is <strong>not</strong> in <code>blacklist</code>. Any integer that is in the mentioned range and not in <code>blacklist</code> should be <strong>equally likely</strong> to be returned.</p>\n\n<p>Optimize your algorithm such that it minimizes the number of calls to the <strong>built-in</strong> random function of your language.</p>\n\n<p>Implement the <code>Solution</code> class:</p>\n\n<ul>\n\t<li><code>Solution(int n, int[] blacklist)</code> Initializes the object with the integer <code>n</code> and the blacklisted integers <code>blacklist</code>.</li>\n\t<li><code>int pick()</code> Returns a random integer in the range <code>[0, n - 1]</code> and not in <code>blacklist</code>.</li>\n</ul>\n\n<p>&nbsp;</p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input</strong>\n[&quot;Solution&quot;, &quot;pick&quot;, &quot;pick&quot;, &quot;pick&quot;, &quot;pick&quot;, &quot;pick&quot;, &quot;pick&quot;, &quot;pick&quot;]\n[[7, [2, 3, 5]], [], [], [], [], [], [], []]\n<strong>Output</strong>\n[null, 0, 4, 1, 6, 1, 0, 4]\n\n<strong>Explanation</strong>\nSolution solution = new Solution(7, [2, 3, 5]);\nsolution.pick(); // return 0, any integer from [0,1,4,6] should be ok. Note that for every call of pick,\n                 // 0, 1, 4, and 6 must be equally likely to be returned (i.e., with probability 1/4).\nsolution.pick(); // return 4\nsolution.pick(); // return 1\nsolution.pick(); // return 6\nsolution.pick(); // return 1\nsolution.pick(); // return 0\nsolution.pick(); // return 4\n</pre>\n\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= n &lt;= 10<sup>9</sup></code></li>\n\t<li><code>0 &lt;= blacklist.length &lt;= min(10<sup>5</sup>, n - 1)</code></li>\n\t<li><code>0 &lt;= blacklist[i] &lt; n</code></li>\n\t<li>All the values of <code>blacklist</code> are <strong>unique</strong>.</li>\n\t<li>At most <code>2 * 10<sup>4</sup></code> calls will be made to <code>pick</code>.</li>\n</ul>\n",
            "translatedTitle": null,
            "translatedContent": null,
            "isPaidOnly": false,
            "difficulty": "Hard",
            "likes": 835,
            "dislikes": 117,
            "isLiked": null,
            "similarQuestions": "[{\"title\": \"Random Pick Index\", \"titleSlug\": \"random-pick-index\", \"difficulty\": \"Medium\", \"translatedTitle\": null}, {\"title\": \"Random Pick with Weight\", \"titleSlug\": \"random-pick-with-weight\", \"difficulty\": \"Medium\", \"translatedTitle\": null}, {\"title\": \"Find Unique Binary String\", \"titleSlug\": \"find-unique-binary-string\", \"difficulty\": \"Medium\", \"translatedTitle\": null}]",
            "exampleTestcases": "[\"Solution\",\"pick\",\"pick\",\"pick\",\"pick\",\"pick\",\"pick\",\"pick\"]\n[[7,[2,3,5]],[],[],[],[],[],[],[]]",
            "categoryTitle": "Algorithms",
            "contributors": [],
            "topicTags": [
                {
                    "name": "Array",
                    "slug": "array",
                    "translatedName": null,
                    "__typename": "TopicTagNode"
                },
                {
                    "name": "Hash Table",
                    "slug": "hash-table",
                    "translatedName": null,
                    "__typename": "TopicTagNode"
                },
                {
                    "name": "Math",
                    "slug": "math",
                    "translatedName": null,
                    "__typename": "TopicTagNode"
                },
                {
                    "name": "Binary Search",
                    "slug": "binary-search",
                    "translatedName": null,
                    "__typename": "TopicTagNode"
                },
                {
                    "name": "Sorting",
                    "slug": "sorting",
                    "translatedName": null,
                    "__typename": "TopicTagNode"
                },
                {
                    "name": "Randomized",
                    "slug": "randomized",
                    "translatedName": null,
                    "__typename": "TopicTagNode"
                }
            ],
            "companyTagStats": null,
            "codeSnippets": [
                {
                    "lang": "C++",
                    "langSlug": "cpp",
                    "code": "class Solution {\npublic:\n    Solution(int n, vector<int>& blacklist) {\n        \n    }\n    \n    int pick() {\n        \n    }\n};\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution* obj = new Solution(n, blacklist);\n * int param_1 = obj->pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Java",
                    "langSlug": "java",
                    "code": "class Solution {\n\n    public Solution(int n, int[] blacklist) {\n        \n    }\n    \n    public int pick() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution obj = new Solution(n, blacklist);\n * int param_1 = obj.pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Python",
                    "langSlug": "python",
                    "code": "class Solution(object):\n\n    def __init__(self, n, blacklist):\n        \"\"\"\n        :type n: int\n        :type blacklist: List[int]\n        \"\"\"\n        \n\n    def pick(self):\n        \"\"\"\n        :rtype: int\n        \"\"\"\n        \n\n\n# Your Solution object will be instantiated and called as such:\n# obj = Solution(n, blacklist)\n# param_1 = obj.pick()",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Python3",
                    "langSlug": "python3",
                    "code": "class Solution:\n\n    def __init__(self, n: int, blacklist: List[int]):\n        \n\n    def pick(self) -> int:\n        \n\n\n# Your Solution object will be instantiated and called as such:\n# obj = Solution(n, blacklist)\n# param_1 = obj.pick()",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "C",
                    "langSlug": "c",
                    "code": "\n\n\ntypedef struct {\n    \n} Solution;\n\n\nSolution* solutionCreate(int n, int* blacklist, int blacklistSize) {\n    \n}\n\nint solutionPick(Solution* obj) {\n    \n}\n\nvoid solutionFree(Solution* obj) {\n    \n}\n\n/**\n * Your Solution struct will be instantiated and called as such:\n * Solution* obj = solutionCreate(n, blacklist, blacklistSize);\n * int param_1 = solutionPick(obj);\n \n * solutionFree(obj);\n*/",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "C#",
                    "langSlug": "csharp",
                    "code": "public class Solution {\n\n    public Solution(int n, int[] blacklist) {\n        \n    }\n    \n    public int Pick() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution obj = new Solution(n, blacklist);\n * int param_1 = obj.Pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "JavaScript",
                    "langSlug": "javascript",
                    "code": "/**\n * @param {number} n\n * @param {number[]} blacklist\n */\nvar Solution = function(n, blacklist) {\n    \n};\n\n/**\n * @return {number}\n */\nSolution.prototype.pick = function() {\n    \n};\n\n/** \n * Your Solution object will be instantiated and called as such:\n * var obj = new Solution(n, blacklist)\n * var param_1 = obj.pick()\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "TypeScript",
                    "langSlug": "typescript",
                    "code": "class Solution {\n    constructor(n: number, blacklist: number[]) {\n        \n    }\n\n    pick(): number {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * var obj = new Solution(n, blacklist)\n * var param_1 = obj.pick()\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "PHP",
                    "langSlug": "php",
                    "code": "class Solution {\n    /**\n     * @param Integer $n\n     * @param Integer[] $blacklist\n     */\n    function __construct($n, $blacklist) {\n        \n    }\n  \n    /**\n     * @return Integer\n     */\n    function pick() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * $obj = Solution($n, $blacklist);\n * $ret_1 = $obj->pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Swift",
                    "langSlug": "swift",
                    "code": "\nclass Solution {\n\n    init(_ n: Int, _ blacklist: [Int]) {\n        \n    }\n    \n    func pick() -> Int {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * let obj = Solution(n, blacklist)\n * let ret_1: Int = obj.pick()\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Kotlin",
                    "langSlug": "kotlin",
                    "code": "class Solution(n: Int, blacklist: IntArray) {\n\n    fun pick(): Int {\n        \n    }\n\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * var obj = Solution(n, blacklist)\n * var param_1 = obj.pick()\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Dart",
                    "langSlug": "dart",
                    "code": "class Solution {\n\n  Solution(int n, List<int> blacklist) {\n    \n  }\n  \n  int pick() {\n    \n  }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution obj = Solution(n, blacklist);\n * int param1 = obj.pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Go",
                    "langSlug": "golang",
                    "code": "type Solution struct {\n    \n}\n\n\nfunc Constructor(n int, blacklist []int) Solution {\n    \n}\n\n\nfunc (this *Solution) Pick() int {\n    \n}\n\n\n/**\n * Your Solution object will be instantiated and called as such:\n * obj := Constructor(n, blacklist);\n * param_1 := obj.Pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Ruby",
                    "langSlug": "ruby",
                    "code": "class Solution\n\n=begin\n    :type n: Integer\n    :type blacklist: Integer[]\n=end\n    def initialize(n, blacklist)\n        \n    end\n\n\n=begin\n    :rtype: Integer\n=end\n    def pick()\n        \n    end\n\n\nend\n\n# Your Solution object will be instantiated and called as such:\n# obj = Solution.new(n, blacklist)\n# param_1 = obj.pick()",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Scala",
                    "langSlug": "scala",
                    "code": "class Solution(_n: Int, _blacklist: Array[Int]) {\n\n    def pick(): Int = {\n        \n    }\n\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * var obj = new Solution(n, blacklist)\n * var param_1 = obj.pick()\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Rust",
                    "langSlug": "rust",
                    "code": "struct Solution {\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 Solution {\n\n    fn new(n: i32, blacklist: Vec<i32>) -> Self {\n        \n    }\n    \n    fn pick(&self) -> i32 {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * let obj = Solution::new(n, blacklist);\n * let ret_1: i32 = obj.pick();\n */",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Racket",
                    "langSlug": "racket",
                    "code": "(define solution%\n  (class object%\n    (super-new)\n    \n    ; n : exact-integer?\n    ; blacklist : (listof exact-integer?)\n    (init-field\n      n\n      blacklist)\n    \n    ; pick : -> exact-integer?\n    (define/public (pick)\n      )))\n\n;; Your solution% object will be instantiated and called as such:\n;; (define obj (new solution% [n n] [blacklist blacklist]))\n;; (define param_1 (send obj pick))",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Erlang",
                    "langSlug": "erlang",
                    "code": "-spec solution_init_(N :: integer(), Blacklist :: [integer()]) -> any().\nsolution_init_(N, Blacklist) ->\n  .\n\n-spec solution_pick() -> integer().\nsolution_pick() ->\n  .\n\n\n%% Your functions will be called as such:\n%% solution_init_(N, Blacklist),\n%% Param_1 = solution_pick(),\n\n%% solution_init_ will be called before every test case, in which you can do some necessary initializations.",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Elixir",
                    "langSlug": "elixir",
                    "code": "defmodule Solution do\n  @spec init_(n :: integer, blacklist :: [integer]) :: any\n  def init_(n, blacklist) do\n    \n  end\n\n  @spec pick() :: integer\n  def pick() do\n    \n  end\nend\n\n# Your functions will be called as such:\n# Solution.init_(n, blacklist)\n# param_1 = Solution.pick()\n\n# Solution.init_ will be called before every test case, in which you can do some necessary initializations.",
                    "__typename": "CodeSnippetNode"
                }
            ],
            "stats": "{\"totalAccepted\": \"39.7K\", \"totalSubmission\": \"119.1K\", \"totalAcceptedRaw\": 39715, \"totalSubmissionRaw\": 119144, \"acRate\": \"33.3%\"}",
            "hints": [],
            "solution": {
                "id": "500",
                "canSeeDetail": false,
                "paidOnly": true,
                "hasVideoSolution": false,
                "paidOnlyVideo": true,
                "__typename": "ArticleNode"
            },
            "status": null,
            "sampleTestCase": "[\"Solution\",\"pick\",\"pick\",\"pick\",\"pick\",\"pick\",\"pick\",\"pick\"]\n[[7,[2,3,5]],[],[],[],[],[],[],[]]",
            "metaData": "{\n  \"classname\": \"Solution\",\n  \"maxbytesperline\": 200000,\n  \"constructor\": {\n    \"params\": [\n      {\n        \"name\": \"n\",\n        \"type\": \"integer\"\n      },\n      {\n        \"name\": \"blacklist\",\n        \"type\": \"integer[]\"\n      },\n      {\n        \"type\": \"integer\",\n        \"name\": \"blacklistSize\",\n        \"lang\": \"c\",\n        \"value\": \"size_2\"\n      }\n    ]\n  },\n  \"methods\": [\n    {\n      \"name\": \"pick\",\n      \"params\": [],\n      \"return\": {\n        \"type\": \"integer\"\n      }\n    }\n  ],\n  \"systemdesign\": true,\n  \"params\": [\n    {\n      \"name\": \"inputs\",\n      \"type\": \"integer[]\"\n    },\n    {\n      \"name\": \"inputs\",\n      \"type\": \"integer[]\"\n    }\n  ],\n  \"return\": {\n    \"type\": \"list<String>\",\n    \"dealloc\": true\n  }\n}",
            "judgerAvailable": true,
            "judgeType": "large",
            "mysqlSchemas": [],
            "enableRunCode": true,
            "enableTestMode": false,
            "enableDebugger": true,
            "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://github.com/datastructures-js/queue/tree/e63563025a5a805aa16928cb53bcd517bfea9230\\\" target=\\\"_blank\\\">datastructures-js/queue</a>.</p>\"], \"ruby\": [\"Ruby\", \"<p><code>Ruby 3.1</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 5.5.2</code>.</p>\"], \"golang\": [\"Go\", \"<p><code>Go 1.21</code></p>\\r\\n<p>Support <a href=\\\"https://github.com/emirpasic/gods/tree/v1.18.1\\\" target=\\\"_blank\\\">https://godoc.org/github.com/emirpasic/gods@v1.18.1</a> library.</p>\"], \"python3\": [\"Python3\", \"<p><code>Python 3.10</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 2.13.7</code>.</p>\"], \"kotlin\": [\"Kotlin\", \"<p><code>Kotlin 1.9.0</code>.</p>\"], \"rust\": [\"Rust\", \"<p><code>Rust 1.58.1</code></p>\\r\\n\\r\\n<p>Supports <a href=\\\"https://crates.io/crates/rand\\\" target=\\\"_blank\\\">rand </a> v0.6\\u00a0from crates.io</p>\"], \"php\": [\"PHP\", \"<p><code>PHP 8.1</code>.</p>\\r\\n<p>With bcmath module</p>\"], \"typescript\": [\"Typescript\", \"<p><code>TypeScript 5.1.6, 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 ES2022 features</a>.</p>\\r\\n\\r\\n<p><a href=\\\"https://lodash.com\\\" target=\\\"_blank\\\">lodash.js</a> library is included by default.</p>\"], \"racket\": [\"Racket\", \"<p>Run with <code>Racket 8.3</code>.</p>\"], \"erlang\": [\"Erlang\", \"Erlang/OTP 25.0\"], \"elixir\": [\"Elixir\", \"Elixir 1.13.4 with Erlang/OTP 25.0\"], \"dart\": [\"Dart\", \"<p>Dart 2.17.3</p>\\r\\n\\r\\n<p>Your code will be run directly without compiling</p>\"]}",
            "libraryUrl": null,
            "adminUrl": null,
            "challengeQuestion": null,
            "__typename": "QuestionNode"
        }
    }
}