Random Flip Matrix
<p>There is an <code>m x n</code> binary grid <code>matrix</code> with all the values set <code>0</code> initially. Design an algorithm to randomly pick an index <code>(i, j)</code> where <code>matrix[i][j] == 0</code> and flips it to <code>1</code>. All the indices <code>(i, j)</code> where <code>matrix[i][j] == 0</code> should be equally likely to be returned.</p>

<p>Optimize your algorithm to minimize the number of calls made to the <strong>built-in</strong> random function of your language and optimize the time and space complexity.</p>

<p>Implement the <code>Solution</code> class:</p>

<ul>
	<li><code>Solution(int m, int n)</code> Initializes the object with the size of the binary matrix <code>m</code> and <code>n</code>.</li>
	<li><code>int[] flip()</code> Returns a random index <code>[i, j]</code> of the matrix where <code>matrix[i][j] == 0</code> and flips it to <code>1</code>.</li>
	<li><code>void reset()</code> Resets all the values of the matrix to be <code>0</code>.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input</strong>
[&quot;Solution&quot;, &quot;flip&quot;, &quot;flip&quot;, &quot;flip&quot;, &quot;reset&quot;, &quot;flip&quot;]
[[3, 1], [], [], [], [], []]
<strong>Output</strong>
[null, [1, 0], [2, 0], [0, 0], null, [2, 0]]

<strong>Explanation</strong>
Solution solution = new Solution(3, 1);
solution.flip();  // return [1, 0], [0,0], [1,0], and [2,0] should be equally likely to be returned.
solution.flip();  // return [2, 0], Since [1,0] was returned, [2,0] and [0,0]
solution.flip();  // return [0, 0], Based on the previously returned indices, only [0,0] can be returned.
solution.reset(); // All the values are reset to 0 and can be returned.
solution.flip();  // return [2, 0], [0,0], [1,0], and [2,0] should be equally likely to be returned.
</pre>

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

<ul>
	<li><code>1 &lt;= m, n &lt;= 10<sup>4</sup></code></li>
	<li>There will be at least one free cell for each call to <code>flip</code>.</li>
	<li>At most <code>1000</code> calls will be made to <code>flip</code> and <code>reset</code>.</li>
</ul>

[]
[]
[{"value": "cpp", "text": "C++", "defaultCode": "class Solution {\npublic:\n    Solution(int m, int n) {\n        \n    }\n    \n    vector<int> flip() {\n        \n    }\n    \n    void reset() {\n        \n    }\n};\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution* obj = new Solution(m, n);\n * vector<int> param_1 = obj->flip();\n * obj->reset();\n */"}, {"value": "java", "text": "Java", "defaultCode": "class Solution {\n\n    public Solution(int m, int n) {\n        \n    }\n    \n    public int[] flip() {\n        \n    }\n    \n    public void reset() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution obj = new Solution(m, n);\n * int[] param_1 = obj.flip();\n * obj.reset();\n */"}, {"value": "python", "text": "Python", "defaultCode": "class Solution(object):\n\n    def __init__(self, m, n):\n        \"\"\"\n        :type m: int\n        :type n: int\n        \"\"\"\n        \n\n    def flip(self):\n        \"\"\"\n        :rtype: List[int]\n        \"\"\"\n        \n\n    def reset(self):\n        \"\"\"\n        :rtype: None\n        \"\"\"\n        \n\n\n# Your Solution object will be instantiated and called as such:\n# obj = Solution(m, n)\n# param_1 = obj.flip()\n# obj.reset()"}, {"value": "python3", "text": "Python3", "defaultCode": "class Solution:\n\n    def __init__(self, m: int, n: int):\n        \n\n    def flip(self) -> List[int]:\n        \n\n    def reset(self) -> None:\n        \n\n\n# Your Solution object will be instantiated and called as such:\n# obj = Solution(m, n)\n# param_1 = obj.flip()\n# obj.reset()"}, {"value": "c", "text": "C", "defaultCode": "\n\n\ntypedef struct {\n    \n} Solution;\n\n\nSolution* solutionCreate(int m, int n) {\n    \n}\n\nint* solutionFlip(Solution* obj, int* retSize) {\n    \n}\n\nvoid solutionReset(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(m, n);\n * int* param_1 = solutionFlip(obj, retSize);\n \n * solutionReset(obj);\n \n * solutionFree(obj);\n*/"}, {"value": "csharp", "text": "C#", "defaultCode": "public class Solution {\n\n    public Solution(int m, int n) {\n        \n    }\n    \n    public int[] Flip() {\n        \n    }\n    \n    public void Reset() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution obj = new Solution(m, n);\n * int[] param_1 = obj.Flip();\n * obj.Reset();\n */"}, {"value": "javascript", "text": "JavaScript", "defaultCode": "/**\n * @param {number} m\n * @param {number} n\n */\nvar Solution = function(m, n) {\n    \n};\n\n/**\n * @return {number[]}\n */\nSolution.prototype.flip = function() {\n    \n};\n\n/**\n * @return {void}\n */\nSolution.prototype.reset = function() {\n    \n};\n\n/** \n * Your Solution object will be instantiated and called as such:\n * var obj = new Solution(m, n)\n * var param_1 = obj.flip()\n * obj.reset()\n */"}, {"value": "typescript", "text": "TypeScript", "defaultCode": "class Solution {\n    constructor(m: number, n: number) {\n        \n    }\n\n    flip(): number[] {\n        \n    }\n\n    reset(): void {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * var obj = new Solution(m, n)\n * var param_1 = obj.flip()\n * obj.reset()\n */"}, {"value": "php", "text": "PHP", "defaultCode": "class Solution {\n    /**\n     * @param Integer $m\n     * @param Integer $n\n     */\n    function __construct($m, $n) {\n        \n    }\n  \n    /**\n     * @return Integer[]\n     */\n    function flip() {\n        \n    }\n  \n    /**\n     * @return NULL\n     */\n    function reset() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * $obj = Solution($m, $n);\n * $ret_1 = $obj->flip();\n * $obj->reset();\n */"}, {"value": "swift", "text": "Swift", "defaultCode": "\nclass Solution {\n\n    init(_ m: Int, _ n: Int) {\n        \n    }\n    \n    func flip() -> [Int] {\n        \n    }\n    \n    func reset() {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * let obj = Solution(m, n)\n * let ret_1: [Int] = obj.flip()\n * obj.reset()\n */"}, {"value": "kotlin", "text": "Kotlin", "defaultCode": "class Solution(m: Int, n: Int) {\n\n    fun flip(): IntArray {\n        \n    }\n\n    fun reset() {\n        \n    }\n\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * var obj = Solution(m, n)\n * var param_1 = obj.flip()\n * obj.reset()\n */"}, {"value": "dart", "text": "Dart", "defaultCode": "class Solution {\n\n  Solution(int m, int n) {\n    \n  }\n  \n  List<int> flip() {\n    \n  }\n  \n  void reset() {\n    \n  }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * Solution obj = Solution(m, n);\n * List<int> param1 = obj.flip();\n * obj.reset();\n */"}, {"value": "golang", "text": "Go", "defaultCode": "type Solution struct {\n    \n}\n\n\nfunc Constructor(m int, n int) Solution {\n    \n}\n\n\nfunc (this *Solution) Flip() []int {\n    \n}\n\n\nfunc (this *Solution) Reset()  {\n    \n}\n\n\n/**\n * Your Solution object will be instantiated and called as such:\n * obj := Constructor(m, n);\n * param_1 := obj.Flip();\n * obj.Reset();\n */"}, {"value": "ruby", "text": "Ruby", "defaultCode": "class Solution\n\n=begin\n    :type m: Integer\n    :type n: Integer\n=end\n    def initialize(m, n)\n        \n    end\n\n\n=begin\n    :rtype: Integer[]\n=end\n    def flip()\n        \n    end\n\n\n=begin\n    :rtype: Void\n=end\n    def reset()\n        \n    end\n\n\nend\n\n# Your Solution object will be instantiated and called as such:\n# obj = Solution.new(m, n)\n# param_1 = obj.flip()\n# obj.reset()"}, {"value": "scala", "text": "Scala", "defaultCode": "class Solution(_m: Int, _n: Int) {\n\n    def flip(): Array[Int] = {\n        \n    }\n\n    def reset(): Unit = {\n        \n    }\n\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * val obj = new Solution(m, n)\n * val param_1 = obj.flip()\n * obj.reset()\n */"}, {"value": "rust", "text": "Rust", "defaultCode": "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(m: i32, n: i32) -> Self {\n        \n    }\n    \n    fn flip(&self) -> Vec<i32> {\n        \n    }\n    \n    fn reset(&self) {\n        \n    }\n}\n\n/**\n * Your Solution object will be instantiated and called as such:\n * let obj = Solution::new(m, n);\n * let ret_1: Vec<i32> = obj.flip();\n * obj.reset();\n */"}, {"value": "racket", "text": "Racket", "defaultCode": "(define solution%\n  (class object%\n    (super-new)\n    \n    ; m : exact-integer?\n    ; n : exact-integer?\n    (init-field\n      m\n      n)\n    \n    ; flip : -> (listof exact-integer?)\n    (define/public (flip)\n      )\n    ; reset : -> void?\n    (define/public (reset)\n      )))\n\n;; Your solution% object will be instantiated and called as such:\n;; (define obj (new solution% [m m] [n n]))\n;; (define param_1 (send obj flip))\n;; (send obj reset)"}, {"value": "erlang", "text": "Erlang", "defaultCode": "-spec solution_init_(M :: integer(), N :: integer()) -> any().\nsolution_init_(M, N) ->\n  .\n\n-spec solution_flip() -> [integer()].\nsolution_flip() ->\n  .\n\n-spec solution_reset() -> any().\nsolution_reset() ->\n  .\n\n\n%% Your functions will be called as such:\n%% solution_init_(M, N),\n%% Param_1 = solution_flip(),\n%% solution_reset(),\n\n%% solution_init_ will be called before every test case, in which you can do some necessary initializations."}, {"value": "elixir", "text": "Elixir", "defaultCode": "defmodule Solution do\n  @spec init_(m :: integer, n :: integer) :: any\n  def init_(m, n) do\n    \n  end\n\n  @spec flip() :: [integer]\n  def flip() do\n    \n  end\n\n  @spec reset() :: any\n  def reset() do\n    \n  end\nend\n\n# Your functions will be called as such:\n# Solution.init_(m, n)\n# param_1 = Solution.flip()\n# Solution.reset()\n\n# Solution.init_ will be called before every test case, in which you can do some necessary initializations."}]
{
  "classname": "Solution",
  "maxbytesperline": 200000,
  "constructor": {
    "params": [
      {
        "name": "m",
        "type": "integer"
      },
      {
        "name": "n",
        "type": "integer"
      }
    ]
  },
  "methods": [
    {
      "name": "flip",
      "params": [],
      "return": {
        "type": "integer[]"
      }
    },
    {
      "name": "reset",
      "params": [],
      "return": {
        "type": "void"
      }
    }
  ],
  "systemdesign": true,
  "params": [
    {
      "name": "inputs",
      "type": "integer[]"
    },
    {
      "name": "inputs",
      "type": "integer[]"
    }
  ],
  "return": {
    "type": "list<String>",
    "dealloc": true
  }
}
{"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>"], "rust": ["Rust", "<p><code>Rust 1.85.0</code>. Your code will be compiled with <code>opt-level</code> 2.</p>\r\n\r\n<p>Supports <a href=\"https://crates.io/crates/rand\" target=\"_blank\">rand v0.8</a> and <a href=\"https://crates.io/crates/regex\" target=\"_blank\">regex\u00a0v1</a> and <a href=\"https://crates.io/crates/itertools\" target=\"_blank\">itertools\u00a0v0.14</a> from crates.io</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>"], "racket": ["Racket", "<p><a href=\"https://docs.racket-lang.org/guide/performance.html#%28tech._c%29\" target=\"_blank\">Racket CS</a> v8.15</p>\r\n\r\n<p>Using <code>#lang racket</code></p>\r\n\r\n<p>Required <code>data/gvector data/queue data/order data/heap</code> automatically for your convenience</p>"], "erlang": ["Erlang", "Erlang/OTP 26"], "elixir": ["Elixir", "Elixir 1.17 with Erlang/OTP 26"], "dart": ["Dart", "<p>Dart 3.2. You may use package <a href=\"https://pub.dev/packages/collection/versions/1.18.0\" target=\"_blank\">collection</a></p>\r\n\r\n<p>Your code will be run directly without compiling</p>"]}
['Hash Table', 'Math', 'Reservoir Sampling', 'Randomized']