{
"data": {
"question": {
"questionId": "1761",
"questionFrontendId": "1641",
"boundTopicId": null,
"title": "Count Sorted Vowel Strings",
"titleSlug": "count-sorted-vowel-strings",
"content": "<p>Given an integer <code>n</code>, return <em>the number of strings of length </em><code>n</code><em> that consist only of vowels (</em><code>a</code><em>, </em><code>e</code><em>, </em><code>i</code><em>, </em><code>o</code><em>, </em><code>u</code><em>) and are <strong>lexicographically sorted</strong>.</em></p>\n\n<p>A string <code>s</code> is <strong>lexicographically sorted</strong> if for all valid <code>i</code>, <code>s[i]</code> is the same as or comes before <code>s[i+1]</code> in the alphabet.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 1\n<strong>Output:</strong> 5\n<strong>Explanation:</strong> The 5 sorted strings that consist of vowels only are <code>["a","e","i","o","u"].</code>\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 2\n<strong>Output:</strong> 15\n<strong>Explanation:</strong> The 15 sorted strings that consist of vowels only are\n["aa","ae","ai","ao","au","ee","ei","eo","eu","ii","io","iu","oo","ou","uu"].\nNote that "ea" is not a valid string since 'e' comes after 'a' in the alphabet.\n</pre>\n\n<p><strong>Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 33\n<strong>Output:</strong> 66045\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= n <= 50</code> </li>\n</ul>\n",
"translatedTitle": null,
"translatedContent": null,
"isPaidOnly": false,
"difficulty": "Medium",
"likes": 1717,
"dislikes": 37,
"isLiked": null,
"similarQuestions": "[]",
"exampleTestcases": "1\n2\n33",
"categoryTitle": "Algorithms",
"contributors": [],
"topicTags": [
{
"name": "Dynamic Programming",
"slug": "dynamic-programming",
"translatedName": null,
"__typename": "TopicTagNode"
}
],
"companyTagStats": null,
"codeSnippets": [
{
"lang": "C++",
"langSlug": "cpp",
"code": "class Solution {\npublic:\n int countVowelStrings(int n) {\n \n }\n};",
"__typename": "CodeSnippetNode"
},
{
"lang": "Java",
"langSlug": "java",
"code": "class Solution {\n public int countVowelStrings(int n) {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Python",
"langSlug": "python",
"code": "class Solution(object):\n def countVowelStrings(self, n):\n \"\"\"\n :type n: int\n :rtype: int\n \"\"\"\n ",
"__typename": "CodeSnippetNode"
},
{
"lang": "Python3",
"langSlug": "python3",
"code": "class Solution:\n def countVowelStrings(self, n: int) -> int:\n ",
"__typename": "CodeSnippetNode"
},
{
"lang": "C",
"langSlug": "c",
"code": "\n\nint countVowelStrings(int n){\n\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "C#",
"langSlug": "csharp",
"code": "public class Solution {\n public int CountVowelStrings(int n) {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "JavaScript",
"langSlug": "javascript",
"code": "/**\n * @param {number} n\n * @return {number}\n */\nvar countVowelStrings = function(n) {\n \n};",
"__typename": "CodeSnippetNode"
},
{
"lang": "Ruby",
"langSlug": "ruby",
"code": "# @param {Integer} n\n# @return {Integer}\ndef count_vowel_strings(n)\n \nend",
"__typename": "CodeSnippetNode"
},
{
"lang": "Swift",
"langSlug": "swift",
"code": "class Solution {\n func countVowelStrings(_ n: Int) -> Int {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Go",
"langSlug": "golang",
"code": "func countVowelStrings(n int) int {\n \n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Scala",
"langSlug": "scala",
"code": "object Solution {\n def countVowelStrings(n: Int): Int = {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Kotlin",
"langSlug": "kotlin",
"code": "class Solution {\n fun countVowelStrings(n: Int): Int {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Rust",
"langSlug": "rust",
"code": "impl Solution {\n pub fn count_vowel_strings(n: i32) -> i32 {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "PHP",
"langSlug": "php",
"code": "class Solution {\n\n /**\n * @param Integer $n\n * @return Integer\n */\n function countVowelStrings($n) {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "TypeScript",
"langSlug": "typescript",
"code": "function countVowelStrings(n: number): number {\n\n};",
"__typename": "CodeSnippetNode"
},
{
"lang": "Racket",
"langSlug": "racket",
"code": "(define/contract (count-vowel-strings n)\n (-> exact-integer? exact-integer?)\n\n )",
"__typename": "CodeSnippetNode"
},
{
"lang": "Erlang",
"langSlug": "erlang",
"code": "-spec count_vowel_strings(N :: integer()) -> integer().\ncount_vowel_strings(N) ->\n .",
"__typename": "CodeSnippetNode"
},
{
"lang": "Elixir",
"langSlug": "elixir",
"code": "defmodule Solution do\n @spec count_vowel_strings(n :: integer) :: integer\n def count_vowel_strings(n) do\n\n end\nend",
"__typename": "CodeSnippetNode"
}
],
"stats": "{\"totalAccepted\": \"81.3K\", \"totalSubmission\": \"108.6K\", \"totalAcceptedRaw\": 81276, \"totalSubmissionRaw\": 108624, \"acRate\": \"74.8%\"}",
"hints": [
"For each character, its possible values will depend on the value of its previous character, because it needs to be not smaller than it.",
"Think backtracking. Build a recursive function count(n, last_character) that counts the number of valid strings of length n and whose first characters are not less than last_character.",
"In this recursive function, iterate on the possible characters for the first character, which will be all the vowels not less than last_character, and for each possible value c, increase the answer by count(n-1, c)."
],
"solution": {
"id": "1041",
"canSeeDetail": false,
"paidOnly": true,
"hasVideoSolution": false,
"paidOnlyVideo": true,
"__typename": "ArticleNode"
},
"status": null,
"sampleTestCase": "1",
"metaData": "{\n \"name\": \"countVowelStrings\",\n \"params\": [\n {\n \"name\": \"n\",\n \"type\": \"integer\"\n }\n ],\n \"return\": {\n \"type\": \"integer\"\n }\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. 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://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-9\\\" target=\\\"_blank\\\">C# 10 with .NET 6 runtime</a></p>\\r\\n\\r\\n<p>Your code is compiled with debug flag enabled (<code>/debug</code>).</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 <a href=\\\"https://github.com/datastructures-js/priority-queue\\\" target=\\\"_blank\\\">datastructures-js/priority-queue</a> and <a href=\\\"https://github.com/datastructures-js/queue\\\" target=\\\"_blank\\\">datastructures-js/queue</a>.</p>\"], \"ruby\": [\"Ruby\", \"<p><code>Ruby 3.1</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 5.5.2</code>.</p>\"], \"golang\": [\"Go\", \"<p><code>Go 1.17.6</code>.</p>\\r\\n\\r\\n<p>Support <a href=\\\"https://godoc.org/github.com/emirpasic/gods\\\" target=\\\"_blank\\\">https://godoc.org/github.com/emirpasic/gods</a> library.</p>\"], \"python3\": [\"Python3\", \"<p><code>Python 3.10</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 2.13.7</code>.</p>\"], \"kotlin\": [\"Kotlin\", \"<p><code>Kotlin 1.3.10</code>.</p>\"], \"rust\": [\"Rust\", \"<p><code>Rust 1.58.1</code></p>\\r\\n\\r\\n<p>Supports <a href=\\\"https://crates.io/crates/rand\\\" target=\\\"_blank\\\">rand </a> v0.6\\u00a0from crates.io</p>\"], \"php\": [\"PHP\", \"<p><code>PHP 8.1</code>.</p>\\r\\n<p>With bcmath module</p>\"], \"typescript\": [\"Typescript\", \"<p><code>TypeScript 4.5.4, 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 ES2020 features</a>.</p>\\r\\n\\r\\n<p><a href=\\\"https://lodash.com\\\" target=\\\"_blank\\\">lodash.js</a> library is included by default.</p>\"], \"racket\": [\"Racket\", \"<p>Run with <code>Racket 8.3</code>.</p>\"], \"erlang\": [\"Erlang\", \"Erlang/OTP 24.2\"], \"elixir\": [\"Elixir\", \"Elixir 1.13.0 with Erlang/OTP 24.2\"]}",
"libraryUrl": null,
"adminUrl": null,
"challengeQuestion": null,
"__typename": "QuestionNode"
}
}
}