{ "data": { "question": { "questionId": "2871", "questionFrontendId": "2816", "boundTopicId": null, "title": "Double a Number Represented as a Linked List", "titleSlug": "double-a-number-represented-as-a-linked-list", "content": "

You are given the head of a non-empty linked list representing a non-negative integer without leading zeroes.

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Return the head of the linked list after doubling it.

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Example 1:

\n\"\"\n
\nInput: head = [1,8,9]\nOutput: [3,7,8]\nExplanation: The figure above corresponds to the given linked list which represents the number 189. Hence, the returned linked list represents the number 189 * 2 = 378.\n
\n\n

Example 2:

\n\"\"\n
\nInput: head = [9,9,9]\nOutput: [1,9,9,8]\nExplanation: The figure above corresponds to the given linked list which represents the number 999. Hence, the returned linked list reprersents the number 999 * 2 = 1998. \n
\n\n

 

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Constraints:

\n\n\n", "translatedTitle": null, "translatedContent": null, "isPaidOnly": false, "difficulty": "Medium", "likes": 403, "dislikes": 6, "isLiked": null, "similarQuestions": "[{\"title\": \"Add Two Numbers\", \"titleSlug\": \"add-two-numbers\", \"difficulty\": \"Medium\", \"translatedTitle\": null}, {\"title\": \"Plus One Linked List\", \"titleSlug\": \"plus-one-linked-list\", \"difficulty\": \"Medium\", \"translatedTitle\": null}]", "exampleTestcases": "[1,8,9]\n[9,9,9]", "categoryTitle": "Algorithms", "contributors": [], "topicTags": [ { "name": "Linked List", "slug": "linked-list", "translatedName": null, "__typename": "TopicTagNode" }, { "name": "Math", "slug": "math", "translatedName": null, "__typename": "TopicTagNode" }, { "name": "Stack", "slug": "stack", "translatedName": null, "__typename": "TopicTagNode" } ], "companyTagStats": null, "codeSnippets": [ { "lang": "C++", "langSlug": "cpp", "code": "/**\n * Definition for singly-linked list.\n * struct ListNode {\n * int val;\n * ListNode *next;\n * ListNode() : val(0), next(nullptr) {}\n * ListNode(int x) : val(x), next(nullptr) {}\n * ListNode(int x, ListNode *next) : val(x), next(next) {}\n * };\n */\nclass Solution {\npublic:\n ListNode* doubleIt(ListNode* head) {\n \n }\n};", "__typename": "CodeSnippetNode" }, { "lang": "Java", "langSlug": "java", "code": "/**\n * Definition for singly-linked list.\n * public class ListNode {\n * int val;\n * ListNode next;\n * ListNode() {}\n * ListNode(int val) { this.val = val; }\n * ListNode(int val, ListNode next) { this.val = val; this.next = next; }\n * }\n */\nclass Solution {\n public ListNode doubleIt(ListNode head) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Python", "langSlug": "python", "code": "# Definition for singly-linked list.\n# class ListNode(object):\n# def __init__(self, val=0, next=None):\n# self.val = val\n# self.next = next\nclass Solution(object):\n def doubleIt(self, head):\n \"\"\"\n :type head: Optional[ListNode]\n :rtype: Optional[ListNode]\n \"\"\"\n ", "__typename": "CodeSnippetNode" }, { "lang": "Python3", "langSlug": "python3", "code": "# Definition for singly-linked list.\n# class ListNode:\n# def __init__(self, val=0, next=None):\n# self.val = val\n# self.next = next\nclass Solution:\n def doubleIt(self, head: Optional[ListNode]) -> Optional[ListNode]:\n ", "__typename": "CodeSnippetNode" }, { "lang": "C", "langSlug": "c", "code": "/**\n * Definition for singly-linked list.\n * struct ListNode {\n * int val;\n * struct ListNode *next;\n * };\n */\nstruct ListNode* doubleIt(struct ListNode* head){\n\n}", "__typename": "CodeSnippetNode" }, { "lang": "C#", "langSlug": "csharp", "code": "/**\n * Definition for singly-linked list.\n * public class ListNode {\n * public int val;\n * public ListNode next;\n * public ListNode(int val=0, ListNode next=null) {\n * this.val = val;\n * this.next = next;\n * }\n * }\n */\npublic class Solution {\n public ListNode DoubleIt(ListNode head) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "JavaScript", "langSlug": "javascript", "code": "/**\n * Definition for singly-linked list.\n * function ListNode(val, next) {\n * this.val = (val===undefined ? 0 : val)\n * this.next = (next===undefined ? null : next)\n * }\n */\n/**\n * @param {ListNode} head\n * @return {ListNode}\n */\nvar doubleIt = function(head) {\n \n};", "__typename": "CodeSnippetNode" }, { "lang": "TypeScript", "langSlug": "typescript", "code": "/**\n * Definition for singly-linked list.\n * class ListNode {\n * val: number\n * next: ListNode | null\n * constructor(val?: number, next?: ListNode | null) {\n * this.val = (val===undefined ? 0 : val)\n * this.next = (next===undefined ? null : next)\n * }\n * }\n */\n\nfunction doubleIt(head: ListNode | null): ListNode | null {\n\n};", "__typename": "CodeSnippetNode" }, { "lang": "PHP", "langSlug": "php", "code": "/**\n * Definition for a singly-linked list.\n * class ListNode {\n * public $val = 0;\n * public $next = null;\n * function __construct($val = 0, $next = null) {\n * $this->val = $val;\n * $this->next = $next;\n * }\n * }\n */\nclass Solution {\n\n /**\n * @param ListNode $head\n * @return ListNode\n */\n function doubleIt($head) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Swift", "langSlug": "swift", "code": "/**\n * Definition for singly-linked list.\n * public class ListNode {\n * public var val: Int\n * public var next: ListNode?\n * public init() { self.val = 0; self.next = nil; }\n * public init(_ val: Int) { self.val = val; self.next = nil; }\n * public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }\n * }\n */\nclass Solution {\n func doubleIt(_ head: ListNode?) -> ListNode? {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Kotlin", "langSlug": "kotlin", "code": "/**\n * Example:\n * var li = ListNode(5)\n * var v = li.`val`\n * Definition for singly-linked list.\n * class ListNode(var `val`: Int) {\n * var next: ListNode? = null\n * }\n */\nclass Solution {\n fun doubleIt(head: ListNode?): ListNode? {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Dart", "langSlug": "dart", "code": "/**\n * Definition for singly-linked list.\n * class ListNode {\n * int val;\n * ListNode? next;\n * ListNode([this.val = 0, this.next]);\n * }\n */\nclass Solution {\n ListNode? doubleIt(ListNode? head) {\n\n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Go", "langSlug": "golang", "code": "/**\n * Definition for singly-linked list.\n * type ListNode struct {\n * Val int\n * Next *ListNode\n * }\n */\nfunc doubleIt(head *ListNode) *ListNode {\n \n}", "__typename": "CodeSnippetNode" }, { "lang": "Ruby", "langSlug": "ruby", "code": "# Definition for singly-linked list.\n# class ListNode\n# attr_accessor :val, :next\n# def initialize(val = 0, _next = nil)\n# @val = val\n# @next = _next\n# end\n# end\n# @param {ListNode} head\n# @return {ListNode}\ndef double_it(head)\n \nend", "__typename": "CodeSnippetNode" }, { "lang": "Scala", "langSlug": "scala", "code": "/**\n * Definition for singly-linked list.\n * class ListNode(_x: Int = 0, _next: ListNode = null) {\n * var next: ListNode = _next\n * var x: Int = _x\n * }\n */\nobject Solution {\n def doubleIt(head: ListNode): ListNode = {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Rust", "langSlug": "rust", "code": "// Definition for singly-linked list.\n// #[derive(PartialEq, Eq, Clone, Debug)]\n// pub struct ListNode {\n// pub val: i32,\n// pub next: Option>\n// }\n// \n// impl ListNode {\n// #[inline]\n// fn new(val: i32) -> Self {\n// ListNode {\n// next: None,\n// val\n// }\n// }\n// }\nimpl Solution {\n pub fn double_it(head: Option>) -> Option> {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Racket", "langSlug": "racket", "code": "; Definition for singly-linked list:\n#|\n\n; val : integer?\n; next : (or/c list-node? #f)\n(struct list-node\n (val next) #:mutable #:transparent)\n\n; constructor\n(define (make-list-node [val 0])\n (list-node val #f))\n\n|#\n\n(define/contract (double-it head)\n (-> (or/c list-node? #f) (or/c list-node? #f))\n\n )", "__typename": "CodeSnippetNode" }, { "lang": "Erlang", "langSlug": "erlang", "code": "%% Definition for singly-linked list.\n%%\n%% -record(list_node, {val = 0 :: integer(),\n%% next = null :: 'null' | #list_node{}}).\n\n-spec double_it(Head :: #list_node{} | null) -> #list_node{} | null.\ndouble_it(Head) ->\n .", "__typename": "CodeSnippetNode" }, { "lang": "Elixir", "langSlug": "elixir", "code": "# Definition for singly-linked list.\n#\n# defmodule ListNode do\n# @type t :: %__MODULE__{\n# val: integer,\n# next: ListNode.t() | nil\n# }\n# defstruct val: 0, next: nil\n# end\n\ndefmodule Solution do\n @spec double_it(head :: ListNode.t | nil) :: ListNode.t | nil\n def double_it(head) do\n\n end\nend", "__typename": "CodeSnippetNode" } ], "stats": "{\"totalAccepted\": \"33.5K\", \"totalSubmission\": \"69.2K\", \"totalAcceptedRaw\": 33453, \"totalSubmissionRaw\": 69164, \"acRate\": \"48.4%\"}", "hints": [ "Traverse the linked list from the least significant digit to the most significant digit and multiply each node's value by 2", "Handle any carry-over digits that may arise during the doubling process.", "If there is a carry-over digit on the most significant digit, create a new node with that value and point it to the start of the given linked list and return it." ], "solution": null, "status": null, "sampleTestCase": "[1,8,9]", "metaData": "{\n \"name\": \"doubleIt\",\n \"params\": [\n {\n \"name\": \"head\",\n \"type\": \"ListNode\"\n }\n ],\n \"return\": {\n \"type\": \"ListNode\"\n }\n}", "judgerAvailable": true, "judgeType": "large", "mysqlSchemas": [], "enableRunCode": true, "enableTestMode": false, "enableDebugger": true, "envInfo": "{\"cpp\": [\"C++\", \"

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Most standard library headers are already included automatically for your convenience.

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Python 2.7.12.

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For Map/TreeMap data structure, you may use sortedcontainers library.

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Note that Python 2.7 will not be maintained past 2020. For the latest Python, please choose Python3 instead.

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