Product of the Last K Numbers
<p>Design an algorithm that accepts a stream of integers and retrieves the product of the last <code>k</code> integers of the stream.</p>

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

<ul>
	<li><code>ProductOfNumbers()</code> Initializes the object with an empty stream.</li>
	<li><code>void add(int num)</code> Appends the integer <code>num</code> to the stream.</li>
	<li><code>int getProduct(int k)</code> Returns the product of the last <code>k</code> numbers in the current list. You can assume that always the current list has at least <code>k</code> numbers.</li>
</ul>

<p>The test cases are generated so that, at any time, the product of any contiguous sequence of numbers will fit into a single 32-bit integer without overflowing.</p>

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

<pre>
<strong>Input</strong>
[&quot;ProductOfNumbers&quot;,&quot;add&quot;,&quot;add&quot;,&quot;add&quot;,&quot;add&quot;,&quot;add&quot;,&quot;getProduct&quot;,&quot;getProduct&quot;,&quot;getProduct&quot;,&quot;add&quot;,&quot;getProduct&quot;]
[[],[3],[0],[2],[5],[4],[2],[3],[4],[8],[2]]

<strong>Output</strong>
[null,null,null,null,null,null,20,40,0,null,32]

<strong>Explanation</strong>
ProductOfNumbers productOfNumbers = new ProductOfNumbers();
productOfNumbers.add(3);        // [3]
productOfNumbers.add(0);        // [3,0]
productOfNumbers.add(2);        // [3,0,2]
productOfNumbers.add(5);        // [3,0,2,5]
productOfNumbers.add(4);        // [3,0,2,5,4]
productOfNumbers.getProduct(2); // return 20. The product of the last 2 numbers is 5 * 4 = 20
productOfNumbers.getProduct(3); // return 40. The product of the last 3 numbers is 2 * 5 * 4 = 40
productOfNumbers.getProduct(4); // return 0. The product of the last 4 numbers is 0 * 2 * 5 * 4 = 0
productOfNumbers.add(8);        // [3,0,2,5,4,8]
productOfNumbers.getProduct(2); // return 32. The product of the last 2 numbers is 4 * 8 = 32 
</pre>

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

<ul>
	<li><code>0 &lt;= num &lt;= 100</code></li>
	<li><code>1 &lt;= k &lt;= 4 * 10<sup>4</sup></code></li>
	<li>At most <code>4 * 10<sup>4</sup></code> calls will be made to <code>add</code> and <code>getProduct</code>.</li>
	<li>The product of the stream at any point in time will fit in a <strong>32-bit</strong> integer.</li>
</ul>

<p>&nbsp;</p>
<strong>Follow-up: </strong>Can you implement <strong>both</strong> <code>GetProduct</code> and <code>Add</code> to work in <code>O(1)</code> time complexity instead of <code>O(k)</code> time complexity?
[]
[]
[{"value": "cpp", "text": "C++", "defaultCode": "class ProductOfNumbers {\npublic:\n    ProductOfNumbers() {\n        \n    }\n    \n    void add(int num) {\n        \n    }\n    \n    int getProduct(int k) {\n        \n    }\n};\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * ProductOfNumbers* obj = new ProductOfNumbers();\n * obj->add(num);\n * int param_2 = obj->getProduct(k);\n */"}, {"value": "java", "text": "Java", "defaultCode": "class ProductOfNumbers {\n\n    public ProductOfNumbers() {\n        \n    }\n    \n    public void add(int num) {\n        \n    }\n    \n    public int getProduct(int k) {\n        \n    }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * ProductOfNumbers obj = new ProductOfNumbers();\n * obj.add(num);\n * int param_2 = obj.getProduct(k);\n */"}, {"value": "python", "text": "Python", "defaultCode": "class ProductOfNumbers(object):\n\n    def __init__(self):\n        \n\n    def add(self, num):\n        \"\"\"\n        :type num: int\n        :rtype: None\n        \"\"\"\n        \n\n    def getProduct(self, k):\n        \"\"\"\n        :type k: int\n        :rtype: int\n        \"\"\"\n        \n\n\n# Your ProductOfNumbers object will be instantiated and called as such:\n# obj = ProductOfNumbers()\n# obj.add(num)\n# param_2 = obj.getProduct(k)"}, {"value": "python3", "text": "Python3", "defaultCode": "class ProductOfNumbers:\n\n    def __init__(self):\n        \n\n    def add(self, num: int) -> None:\n        \n\n    def getProduct(self, k: int) -> int:\n        \n\n\n# Your ProductOfNumbers object will be instantiated and called as such:\n# obj = ProductOfNumbers()\n# obj.add(num)\n# param_2 = obj.getProduct(k)"}, {"value": "c", "text": "C", "defaultCode": "\n\n\ntypedef struct {\n    \n} ProductOfNumbers;\n\n\nProductOfNumbers* productOfNumbersCreate() {\n    \n}\n\nvoid productOfNumbersAdd(ProductOfNumbers* obj, int num) {\n    \n}\n\nint productOfNumbersGetProduct(ProductOfNumbers* obj, int k) {\n    \n}\n\nvoid productOfNumbersFree(ProductOfNumbers* obj) {\n    \n}\n\n/**\n * Your ProductOfNumbers struct will be instantiated and called as such:\n * ProductOfNumbers* obj = productOfNumbersCreate();\n * productOfNumbersAdd(obj, num);\n \n * int param_2 = productOfNumbersGetProduct(obj, k);\n \n * productOfNumbersFree(obj);\n*/"}, {"value": "csharp", "text": "C#", "defaultCode": "public class ProductOfNumbers {\n\n    public ProductOfNumbers() {\n        \n    }\n    \n    public void Add(int num) {\n        \n    }\n    \n    public int GetProduct(int k) {\n        \n    }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * ProductOfNumbers obj = new ProductOfNumbers();\n * obj.Add(num);\n * int param_2 = obj.GetProduct(k);\n */"}, {"value": "javascript", "text": "JavaScript", "defaultCode": "\nvar ProductOfNumbers = function() {\n    \n};\n\n/** \n * @param {number} num\n * @return {void}\n */\nProductOfNumbers.prototype.add = function(num) {\n    \n};\n\n/** \n * @param {number} k\n * @return {number}\n */\nProductOfNumbers.prototype.getProduct = function(k) {\n    \n};\n\n/** \n * Your ProductOfNumbers object will be instantiated and called as such:\n * var obj = new ProductOfNumbers()\n * obj.add(num)\n * var param_2 = obj.getProduct(k)\n */"}, {"value": "typescript", "text": "TypeScript", "defaultCode": "class ProductOfNumbers {\n    constructor() {\n        \n    }\n\n    add(num: number): void {\n        \n    }\n\n    getProduct(k: number): number {\n        \n    }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * var obj = new ProductOfNumbers()\n * obj.add(num)\n * var param_2 = obj.getProduct(k)\n */"}, {"value": "php", "text": "PHP", "defaultCode": "class ProductOfNumbers {\n    /**\n     */\n    function __construct() {\n        \n    }\n  \n    /**\n     * @param Integer $num\n     * @return NULL\n     */\n    function add($num) {\n        \n    }\n  \n    /**\n     * @param Integer $k\n     * @return Integer\n     */\n    function getProduct($k) {\n        \n    }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * $obj = ProductOfNumbers();\n * $obj->add($num);\n * $ret_2 = $obj->getProduct($k);\n */"}, {"value": "swift", "text": "Swift", "defaultCode": "\nclass ProductOfNumbers {\n\n    init() {\n        \n    }\n    \n    func add(_ num: Int) {\n        \n    }\n    \n    func getProduct(_ k: Int) -> Int {\n        \n    }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * let obj = ProductOfNumbers()\n * obj.add(num)\n * let ret_2: Int = obj.getProduct(k)\n */"}, {"value": "kotlin", "text": "Kotlin", "defaultCode": "class ProductOfNumbers() {\n\n    fun add(num: Int) {\n        \n    }\n\n    fun getProduct(k: Int): Int {\n        \n    }\n\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * var obj = ProductOfNumbers()\n * obj.add(num)\n * var param_2 = obj.getProduct(k)\n */"}, {"value": "dart", "text": "Dart", "defaultCode": "class ProductOfNumbers {\n\n  ProductOfNumbers() {\n    \n  }\n  \n  void add(int num) {\n    \n  }\n  \n  int getProduct(int k) {\n    \n  }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * ProductOfNumbers obj = ProductOfNumbers();\n * obj.add(num);\n * int param2 = obj.getProduct(k);\n */"}, {"value": "golang", "text": "Go", "defaultCode": "type ProductOfNumbers struct {\n    \n}\n\n\nfunc Constructor() ProductOfNumbers {\n    \n}\n\n\nfunc (this *ProductOfNumbers) Add(num int)  {\n    \n}\n\n\nfunc (this *ProductOfNumbers) GetProduct(k int) int {\n    \n}\n\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * obj := Constructor();\n * obj.Add(num);\n * param_2 := obj.GetProduct(k);\n */"}, {"value": "ruby", "text": "Ruby", "defaultCode": "class ProductOfNumbers\n    def initialize()\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 k: Integer\n    :rtype: Integer\n=end\n    def get_product(k)\n        \n    end\n\n\nend\n\n# Your ProductOfNumbers object will be instantiated and called as such:\n# obj = ProductOfNumbers.new()\n# obj.add(num)\n# param_2 = obj.get_product(k)"}, {"value": "scala", "text": "Scala", "defaultCode": "class ProductOfNumbers() {\n\n    def add(num: Int): Unit = {\n        \n    }\n\n    def getProduct(k: Int): Int = {\n        \n    }\n\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * val obj = new ProductOfNumbers()\n * obj.add(num)\n * val param_2 = obj.getProduct(k)\n */"}, {"value": "rust", "text": "Rust", "defaultCode": "struct ProductOfNumbers {\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 ProductOfNumbers {\n\n    fn new() -> Self {\n        \n    }\n    \n    fn add(&self, num: i32) {\n        \n    }\n    \n    fn get_product(&self, k: i32) -> i32 {\n        \n    }\n}\n\n/**\n * Your ProductOfNumbers object will be instantiated and called as such:\n * let obj = ProductOfNumbers::new();\n * obj.add(num);\n * let ret_2: i32 = obj.get_product(k);\n */"}, {"value": "racket", "text": "Racket", "defaultCode": "(define product-of-numbers%\n  (class object%\n    (super-new)\n    \n    (init-field)\n    \n    ; add : exact-integer? -> void?\n    (define/public (add num)\n      )\n    ; get-product : exact-integer? -> exact-integer?\n    (define/public (get-product k)\n      )))\n\n;; Your product-of-numbers% object will be instantiated and called as such:\n;; (define obj (new product-of-numbers%))\n;; (send obj add num)\n;; (define param_2 (send obj get-product k))"}, {"value": "erlang", "text": "Erlang", "defaultCode": "-spec product_of_numbers_init_() -> any().\nproduct_of_numbers_init_() ->\n  .\n\n-spec product_of_numbers_add(Num :: integer()) -> any().\nproduct_of_numbers_add(Num) ->\n  .\n\n-spec product_of_numbers_get_product(K :: integer()) -> integer().\nproduct_of_numbers_get_product(K) ->\n  .\n\n\n%% Your functions will be called as such:\n%% product_of_numbers_init_(),\n%% product_of_numbers_add(Num),\n%% Param_2 = product_of_numbers_get_product(K),\n\n%% product_of_numbers_init_ will be called before every test case, in which you can do some necessary initializations."}, {"value": "elixir", "text": "Elixir", "defaultCode": "defmodule ProductOfNumbers do\n  @spec init_() :: any\n  def init_() do\n    \n  end\n\n  @spec add(num :: integer) :: any\n  def add(num) do\n    \n  end\n\n  @spec get_product(k :: integer) :: integer\n  def get_product(k) do\n    \n  end\nend\n\n# Your functions will be called as such:\n# ProductOfNumbers.init_()\n# ProductOfNumbers.add(num)\n# param_2 = ProductOfNumbers.get_product(k)\n\n# ProductOfNumbers.init_ will be called before every test case, in which you can do some necessary initializations."}]
{
  "classname": "ProductOfNumbers",
  "constructor": {
    "params": []
  },
  "methods": [
    {
      "params": [
        {
          "type": "integer",
          "name": "num"
        }
      ],
      "name": "add",
      "return": {
        "type": "void"
      }
    },
    {
      "params": [
        {
          "type": "integer",
          "name": "k"
        }
      ],
      "name": "getProduct",
      "return": {
        "type": "integer"
      }
    }
  ],
  "return": {
    "type": "boolean"
  },
  "systemdesign": 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>"]}
['Array', 'Math', 'Design', 'Data Stream', 'Prefix Sum']