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            "title": "Iterator for Combination",
            "titleSlug": "iterator-for-combination",
            "content": "<p>Design the <code>CombinationIterator</code> class:</p>\n\n<ul>\n\t<li><code>CombinationIterator(string characters, int combinationLength)</code> Initializes the object with a string <code>characters</code> of <strong>sorted distinct</strong> lowercase English letters and a number <code>combinationLength</code> as arguments.</li>\n\t<li><code>next()</code> Returns the next combination of length <code>combinationLength</code> in <strong>lexicographical order</strong>.</li>\n\t<li><code>hasNext()</code> Returns <code>true</code> if and only if there exists a next combination.</li>\n</ul>\n\n<p>&nbsp;</p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input</strong>\n[&quot;CombinationIterator&quot;, &quot;next&quot;, &quot;hasNext&quot;, &quot;next&quot;, &quot;hasNext&quot;, &quot;next&quot;, &quot;hasNext&quot;]\n[[&quot;abc&quot;, 2], [], [], [], [], [], []]\n<strong>Output</strong>\n[null, &quot;ab&quot;, true, &quot;ac&quot;, true, &quot;bc&quot;, false]\n\n<strong>Explanation</strong>\nCombinationIterator itr = new CombinationIterator(&quot;abc&quot;, 2);\nitr.next();    // return &quot;ab&quot;\nitr.hasNext(); // return True\nitr.next();    // return &quot;ac&quot;\nitr.hasNext(); // return True\nitr.next();    // return &quot;bc&quot;\nitr.hasNext(); // return False\n</pre>\n\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= combinationLength &lt;= characters.length &lt;= 15</code></li>\n\t<li>All the characters of <code>characters</code> are <strong>unique</strong>.</li>\n\t<li>At most <code>10<sup>4</sup></code> calls will be made to <code>next</code> and <code>hasNext</code>.</li>\n\t<li>It is guaranteed that all calls of the function <code>next</code> are valid.</li>\n</ul>\n",
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                {
                    "lang": "C++",
                    "langSlug": "cpp",
                    "code": "class CombinationIterator {\npublic:\n    CombinationIterator(string characters, int combinationLength) {\n        \n    }\n    \n    string next() {\n        \n    }\n    \n    bool hasNext() {\n        \n    }\n};\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * CombinationIterator* obj = new CombinationIterator(characters, combinationLength);\n * string param_1 = obj->next();\n * bool param_2 = obj->hasNext();\n */",
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                    "lang": "Java",
                    "langSlug": "java",
                    "code": "class CombinationIterator {\n\n    public CombinationIterator(String characters, int combinationLength) {\n        \n    }\n    \n    public String next() {\n        \n    }\n    \n    public boolean hasNext() {\n        \n    }\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * CombinationIterator obj = new CombinationIterator(characters, combinationLength);\n * String param_1 = obj.next();\n * boolean param_2 = obj.hasNext();\n */",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "Python",
                    "langSlug": "python",
                    "code": "class CombinationIterator(object):\n\n    def __init__(self, characters, combinationLength):\n        \"\"\"\n        :type characters: str\n        :type combinationLength: int\n        \"\"\"\n        \n\n    def next(self):\n        \"\"\"\n        :rtype: str\n        \"\"\"\n        \n\n    def hasNext(self):\n        \"\"\"\n        :rtype: bool\n        \"\"\"\n        \n\n\n# Your CombinationIterator object will be instantiated and called as such:\n# obj = CombinationIterator(characters, combinationLength)\n# param_1 = obj.next()\n# param_2 = obj.hasNext()",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Python3",
                    "langSlug": "python3",
                    "code": "class CombinationIterator:\n\n    def __init__(self, characters: str, combinationLength: int):\n        \n\n    def next(self) -> str:\n        \n\n    def hasNext(self) -> bool:\n        \n\n\n# Your CombinationIterator object will be instantiated and called as such:\n# obj = CombinationIterator(characters, combinationLength)\n# param_1 = obj.next()\n# param_2 = obj.hasNext()",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "C",
                    "langSlug": "c",
                    "code": "\n\n\ntypedef struct {\n    \n} CombinationIterator;\n\n\nCombinationIterator* combinationIteratorCreate(char * characters, int combinationLength) {\n    \n}\n\nchar * combinationIteratorNext(CombinationIterator* obj) {\n  \n}\n\nbool combinationIteratorHasNext(CombinationIterator* obj) {\n  \n}\n\nvoid combinationIteratorFree(CombinationIterator* obj) {\n    \n}\n\n/**\n * Your CombinationIterator struct will be instantiated and called as such:\n * CombinationIterator* obj = combinationIteratorCreate(characters, combinationLength);\n * char * param_1 = combinationIteratorNext(obj);\n \n * bool param_2 = combinationIteratorHasNext(obj);\n \n * combinationIteratorFree(obj);\n*/",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "C#",
                    "langSlug": "csharp",
                    "code": "public class CombinationIterator {\n\n    public CombinationIterator(string characters, int combinationLength) {\n        \n    }\n    \n    public string Next() {\n        \n    }\n    \n    public bool HasNext() {\n        \n    }\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * CombinationIterator obj = new CombinationIterator(characters, combinationLength);\n * string param_1 = obj.Next();\n * bool param_2 = obj.HasNext();\n */",
                    "__typename": "CodeSnippetNode"
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                    "lang": "JavaScript",
                    "langSlug": "javascript",
                    "code": "/**\n * @param {string} characters\n * @param {number} combinationLength\n */\nvar CombinationIterator = function(characters, combinationLength) {\n    \n};\n\n/**\n * @return {string}\n */\nCombinationIterator.prototype.next = function() {\n    \n};\n\n/**\n * @return {boolean}\n */\nCombinationIterator.prototype.hasNext = function() {\n    \n};\n\n/** \n * Your CombinationIterator object will be instantiated and called as such:\n * var obj = new CombinationIterator(characters, combinationLength)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "Ruby",
                    "langSlug": "ruby",
                    "code": "class CombinationIterator\n\n=begin\n    :type characters: String\n    :type combination_length: Integer\n=end\n    def initialize(characters, combination_length)\n        \n    end\n\n\n=begin\n    :rtype: String\n=end\n    def next()\n        \n    end\n\n\n=begin\n    :rtype: Boolean\n=end\n    def has_next()\n        \n    end\n\n\nend\n\n# Your CombinationIterator object will be instantiated and called as such:\n# obj = CombinationIterator.new(characters, combination_length)\n# param_1 = obj.next()\n# param_2 = obj.has_next()",
                    "__typename": "CodeSnippetNode"
                },
                {
                    "lang": "Swift",
                    "langSlug": "swift",
                    "code": "\nclass CombinationIterator {\n\n    init(_ characters: String, _ combinationLength: Int) {\n        \n    }\n    \n    func next() -> String {\n        \n    }\n    \n    func hasNext() -> Bool {\n        \n    }\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * let obj = CombinationIterator(characters, combinationLength)\n * let ret_1: String = obj.next()\n * let ret_2: Bool = obj.hasNext()\n */",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "Go",
                    "langSlug": "golang",
                    "code": "type CombinationIterator struct {\n    \n}\n\n\nfunc Constructor(characters string, combinationLength int) CombinationIterator {\n    \n}\n\n\nfunc (this *CombinationIterator) Next() string {\n    \n}\n\n\nfunc (this *CombinationIterator) HasNext() bool {\n    \n}\n\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * obj := Constructor(characters, combinationLength);\n * param_1 := obj.Next();\n * param_2 := obj.HasNext();\n */",
                    "__typename": "CodeSnippetNode"
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                    "lang": "Scala",
                    "langSlug": "scala",
                    "code": "class CombinationIterator(_characters: String, _combinationLength: Int) {\n\n    def next(): String = {\n        \n    }\n\n    def hasNext(): Boolean = {\n        \n    }\n\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * var obj = new CombinationIterator(characters, combinationLength)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "Kotlin",
                    "langSlug": "kotlin",
                    "code": "class CombinationIterator(characters: String, combinationLength: Int) {\n\n    fun next(): String {\n        \n    }\n\n    fun hasNext(): Boolean {\n        \n    }\n\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * var obj = CombinationIterator(characters, combinationLength)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
                    "__typename": "CodeSnippetNode"
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                    "lang": "Rust",
                    "langSlug": "rust",
                    "code": "struct CombinationIterator {\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 CombinationIterator {\n\n    fn new(characters: String, combinationLength: i32) -> Self {\n        \n    }\n    \n    fn next(&self) -> String {\n        \n    }\n    \n    fn has_next(&self) -> bool {\n        \n    }\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * let obj = CombinationIterator::new(characters, combinationLength);\n * let ret_1: String = obj.next();\n * let ret_2: bool = obj.has_next();\n */",
                    "__typename": "CodeSnippetNode"
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                    "lang": "PHP",
                    "langSlug": "php",
                    "code": "class CombinationIterator {\n    /**\n     * @param String $characters\n     * @param Integer $combinationLength\n     */\n    function __construct($characters, $combinationLength) {\n        \n    }\n  \n    /**\n     * @return String\n     */\n    function next() {\n        \n    }\n  \n    /**\n     * @return Boolean\n     */\n    function hasNext() {\n        \n    }\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * $obj = CombinationIterator($characters, $combinationLength);\n * $ret_1 = $obj->next();\n * $ret_2 = $obj->hasNext();\n */",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "TypeScript",
                    "langSlug": "typescript",
                    "code": "class CombinationIterator {\n    constructor(characters: string, combinationLength: number) {\n\n    }\n\n    next(): string {\n\n    }\n\n    hasNext(): boolean {\n\n    }\n}\n\n/**\n * Your CombinationIterator object will be instantiated and called as such:\n * var obj = new CombinationIterator(characters, combinationLength)\n * var param_1 = obj.next()\n * var param_2 = obj.hasNext()\n */",
                    "__typename": "CodeSnippetNode"
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                {
                    "lang": "Racket",
                    "langSlug": "racket",
                    "code": "(define combination-iterator%\n  (class object%\n    (super-new)\n\n    ; characters : string?\n\n    ; combination-length : exact-integer?\n    (init-field\n      characters\n      combination-length)\n    \n    ; next : -> string?\n    (define/public (next)\n\n      )\n    ; has-next : -> boolean?\n    (define/public (has-next)\n\n      )))\n\n;; Your combination-iterator% object will be instantiated and called as such:\n;; (define obj (new combination-iterator% [characters characters] [combination-length combination-length]))\n;; (define param_1 (send obj next))\n;; (define param_2 (send obj has-next))",
                    "__typename": "CodeSnippetNode"
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                    "lang": "Erlang",
                    "langSlug": "erlang",
                    "code": "-spec combination_iterator_init_(Characters :: unicode:unicode_binary(), CombinationLength :: integer()) -> any().\ncombination_iterator_init_(Characters, CombinationLength) ->\n  .\n\n-spec combination_iterator_next() -> unicode:unicode_binary().\ncombination_iterator_next() ->\n  .\n\n-spec combination_iterator_has_next() -> boolean().\ncombination_iterator_has_next() ->\n  .\n\n\n%% Your functions will be called as such:\n%% combination_iterator_init_(Characters, CombinationLength),\n%% Param_1 = combination_iterator_next(),\n%% Param_2 = combination_iterator_has_next(),\n\n%% combination_iterator_init_ will be called before every test case, in which you can do some necessary initializations.",
                    "__typename": "CodeSnippetNode"
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                    "lang": "Elixir",
                    "langSlug": "elixir",
                    "code": "defmodule CombinationIterator do\n  @spec init_(characters :: String.t, combination_length :: integer) :: any\n  def init_(characters, combination_length) do\n\n  end\n\n  @spec next() :: String.t\n  def next() do\n\n  end\n\n  @spec has_next() :: boolean\n  def has_next() do\n\n  end\nend\n\n# Your functions will be called as such:\n# CombinationIterator.init_(characters, combination_length)\n# param_1 = CombinationIterator.next()\n# param_2 = CombinationIterator.has_next()\n\n# CombinationIterator.init_ will be called before every test case, in which you can do some necessary initializations.",
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            "hints": [
                "Generate all combinations as a preprocessing.",
                "Use bit masking to generate all the combinations."
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