{ "data": { "question": { "questionId": "17", "questionFrontendId": "17", "boundTopicId": null, "title": "Letter Combinations of a Phone Number", "titleSlug": "letter-combinations-of-a-phone-number", "content": "<p>Given a string containing digits from <code>2-9</code> inclusive, return all possible letter combinations that the number could represent. Return the answer in <strong>any order</strong>.</p>\n\n<p>A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.</p>\n\n<p><img src=\"https://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Telephone-keypad2.svg/200px-Telephone-keypad2.svg.png\" style=\"width: 200px; height: 162px;\" /></p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> digits = "23"\n<strong>Output:</strong> ["ad","ae","af","bd","be","bf","cd","ce","cf"]\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> digits = ""\n<strong>Output:</strong> []\n</pre>\n\n<p><strong>Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> digits = "2"\n<strong>Output:</strong> ["a","b","c"]\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= digits.length <= 4</code></li>\n\t<li><code>digits[i]</code> is a digit in the range <code>['2', '9']</code>.</li>\n</ul>\n", "translatedTitle": null, "translatedContent": null, "isPaidOnly": false, "difficulty": "Medium", "likes": 9423, "dislikes": 657, "isLiked": null, "similarQuestions": "[{\"title\": \"Generate Parentheses\", \"titleSlug\": \"generate-parentheses\", \"difficulty\": \"Medium\", \"translatedTitle\": null}, {\"title\": \"Combination Sum\", \"titleSlug\": \"combination-sum\", \"difficulty\": \"Medium\", \"translatedTitle\": null}, {\"title\": \"Binary Watch\", \"titleSlug\": \"binary-watch\", \"difficulty\": \"Easy\", \"translatedTitle\": null}]", "exampleTestcases": "\"23\"\n\"\"\n\"2\"", "categoryTitle": "Algorithms", "contributors": [], "topicTags": [ { "name": "Hash Table", "slug": "hash-table", "translatedName": null, "__typename": "TopicTagNode" }, { "name": "String", "slug": "string", "translatedName": null, "__typename": "TopicTagNode" }, { "name": "Backtracking", "slug": "backtracking", "translatedName": null, "__typename": "TopicTagNode" } ], "companyTagStats": null, "codeSnippets": [ { "lang": "C++", "langSlug": "cpp", "code": "class Solution {\npublic:\n vector<string> letterCombinations(string digits) {\n \n }\n};", "__typename": "CodeSnippetNode" }, { "lang": "Java", "langSlug": "java", "code": "class Solution {\n public List<String> letterCombinations(String digits) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Python", "langSlug": "python", "code": "class Solution(object):\n def letterCombinations(self, digits):\n \"\"\"\n :type digits: str\n :rtype: List[str]\n \"\"\"\n ", "__typename": "CodeSnippetNode" }, { "lang": "Python3", "langSlug": "python3", "code": "class Solution:\n def letterCombinations(self, digits: str) -> List[str]:\n ", "__typename": "CodeSnippetNode" }, { "lang": "C", "langSlug": "c", "code": "\n\n/**\n * Note: The returned array must be malloced, assume caller calls free().\n */\nchar ** letterCombinations(char * digits, int* returnSize){\n\n}", "__typename": "CodeSnippetNode" }, { "lang": "C#", "langSlug": "csharp", "code": "public class Solution {\n public IList<string> LetterCombinations(string digits) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "JavaScript", "langSlug": "javascript", "code": "/**\n * @param {string} digits\n * @return {string[]}\n */\nvar letterCombinations = function(digits) {\n \n};", "__typename": "CodeSnippetNode" }, { "lang": "Ruby", "langSlug": "ruby", "code": "# @param {String} digits\n# @return {String[]}\ndef letter_combinations(digits)\n \nend", "__typename": "CodeSnippetNode" }, { "lang": "Swift", "langSlug": "swift", "code": "class Solution {\n func letterCombinations(_ digits: String) -> [String] {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Go", "langSlug": "golang", "code": "func letterCombinations(digits string) []string {\n \n}", "__typename": "CodeSnippetNode" }, { "lang": "Scala", "langSlug": "scala", "code": "object Solution {\n def letterCombinations(digits: String): List[String] = {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Kotlin", "langSlug": "kotlin", "code": "class Solution {\n fun letterCombinations(digits: String): List<String> {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Rust", "langSlug": "rust", "code": "impl Solution {\n pub fn letter_combinations(digits: String) -> Vec<String> {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "PHP", "langSlug": "php", "code": "class Solution {\n\n /**\n * @param String $digits\n * @return String[]\n */\n function letterCombinations($digits) {\n \n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "TypeScript", "langSlug": "typescript", "code": "function letterCombinations(digits: string): string[] {\n\n};", "__typename": "CodeSnippetNode" }, { "lang": "Racket", "langSlug": "racket", "code": "(define/contract (letter-combinations digits)\n (-> string? (listof string?))\n\n )", "__typename": "CodeSnippetNode" }, { "lang": "Erlang", "langSlug": "erlang", "code": "-spec letter_combinations(Digits :: unicode:unicode_binary()) -> [unicode:unicode_binary()].\nletter_combinations(Digits) ->\n .", "__typename": "CodeSnippetNode" }, { "lang": "Elixir", "langSlug": "elixir", "code": "defmodule Solution do\n @spec letter_combinations(digits :: String.t) :: [String.t]\n def letter_combinations(digits) do\n\n end\nend", "__typename": "CodeSnippetNode" } ], "stats": "{\"totalAccepted\": \"1.1M\", \"totalSubmission\": \"2.1M\", \"totalAcceptedRaw\": 1130233, \"totalSubmissionRaw\": 2119169, \"acRate\": \"53.3%\"}", "hints": [], "solution": { "id": "1118", "canSeeDetail": false, "paidOnly": true, "hasVideoSolution": false, "paidOnlyVideo": true, "__typename": "ArticleNode" }, "status": null, "sampleTestCase": "\"23\"", "metaData": "{ \r\n \"name\": \"letterCombinations\",\r\n \"params\": [\r\n { \r\n \"name\": \"digits\",\r\n \"type\": \"string\"\r\n }\r\n ],\r\n \"return\": {\r\n \"type\": \"list<string>\"\r\n }\r\n}", "judgerAvailable": true, "judgeType": "large", "mysqlSchemas": [], "enableRunCode": true, "enableTestMode": false, "enableDebugger": true, "envInfo": "{\"cpp\": [\"C++\", \"<p>Compiled with <code> clang 11 </code> using the latest C++ 17 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 gnu99 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. 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