"content":"<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>\n\n<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>\n\n<p>Implement the <code>Solution</code> class:</p>\n\n<ul>\n\t<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>\n\t<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>\n\t<li><code>void reset()</code> Resets all the values of the matrix to be <code>0</code>.</li>\n</ul>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input</strong>\n["Solution", "flip", "flip", "flip", "reset", "flip"]\n[[3, 1], [], [], [], [], []]\n<strong>Output</strong>\n[null, [1, 0], [2, 0], [0, 0], null, [2, 0]]\n\n<strong>Explanation</strong>\nSolution solution = new Solution(3, 1);\nsolution.flip(); // return [1, 0], [0,0], [1,0], and [2,0] should be equally likely to be returned.\nsolution.flip(); // return [2, 0], Since [1,0] was returned, [2,0] and [0,0]\nsolution.flip(); // return [0, 0], Based on the previously returned indices, only [0,0] can be returned.\nsolution.reset(); // All the values are reset to 0 and can be returned.\nsolution.flip(); // return [2, 0], [0,0], [1,0], and [2,0] should be equally likely to be returned.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= m, n <= 10<sup>4</sup></code></li>\n\t<li>There will be at least one free cell for each call to <code>flip</code>.</li>\n\t<li>At most <code>1000</code> calls will be made to <code>flip</code> and <code>reset</code>.</li>\n</ul>\n",
"code":"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 */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Java",
"langSlug":"java",
"code":"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 */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Python",
"langSlug":"python",
"code":"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()",
"__typename":"CodeSnippetNode"
},
{
"lang":"Python3",
"langSlug":"python3",
"code":"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()",
"code":"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 */",
"__typename":"CodeSnippetNode"
},
{
"lang":"JavaScript",
"langSlug":"javascript",
"code":"/**\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 */",
"code":"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 */",
"code":"class Solution(_m: Int, _n: Int) {\n\n def flip(): Array[Int] = {\n \n }\n\n def reset() {\n \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 */",
"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(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 */",
"code":"-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.",
"code":"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.",
"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
