{
"data": {
"question": {
"questionId": "338",
"questionFrontendId": "338",
"boundTopicId": null,
"title": "Counting Bits",
"titleSlug": "counting-bits",
"content": "<p>Given an integer <code>n</code>, return <em>an array </em><code>ans</code><em> of length </em><code>n + 1</code><em> such that for each </em><code>i</code><em> </em>(<code>0 <= i <= n</code>)<em>, </em><code>ans[i]</code><em> is the <strong>number of </strong></em><code>1</code><em><strong>'s</strong> in the binary representation of </em><code>i</code>.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 2\n<strong>Output:</strong> [0,1,1]\n<strong>Explanation:</strong>\n0 --> 0\n1 --> 1\n2 --> 10\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 5\n<strong>Output:</strong> [0,1,1,2,1,2]\n<strong>Explanation:</strong>\n0 --> 0\n1 --> 1\n2 --> 10\n3 --> 11\n4 --> 100\n5 --> 101\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= n <= 10<sup>5</sup></code></li>\n</ul>\n\n<p> </p>\n<p><strong>Follow up:</strong></p>\n\n<ul>\n\t<li>It is very easy to come up with a solution with a runtime of <code>O(n log n)</code>. Can you do it in linear time <code>O(n)</code> and possibly in a single pass?</li>\n\t<li>Can you do it without using any built-in function (i.e., like <code>__builtin_popcount</code> in C++)?</li>\n</ul>\n",
"translatedTitle": null,
"translatedContent": null,
"isPaidOnly": false,
"difficulty": "Easy",
"likes": 6671,
"dislikes": 314,
"isLiked": null,
"similarQuestions": "[{\"title\": \"Number of 1 Bits\", \"titleSlug\": \"number-of-1-bits\", \"difficulty\": \"Easy\", \"translatedTitle\": null}]",
"exampleTestcases": "2\n5",
"categoryTitle": "Algorithms",
"contributors": [],
"topicTags": [
{
"name": "Dynamic Programming",
"slug": "dynamic-programming",
"translatedName": null,
"__typename": "TopicTagNode"
},
{
"name": "Bit Manipulation",
"slug": "bit-manipulation",
"translatedName": null,
"__typename": "TopicTagNode"
}
],
"companyTagStats": null,
"codeSnippets": [
{
"lang": "C++",
"langSlug": "cpp",
"code": "class Solution {\npublic:\n vector<int> countBits(int n) {\n \n }\n};",
"__typename": "CodeSnippetNode"
},
{
"lang": "Java",
"langSlug": "java",
"code": "class Solution {\n public int[] countBits(int n) {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Python",
"langSlug": "python",
"code": "class Solution(object):\n def countBits(self, n):\n \"\"\"\n :type n: int\n :rtype: List[int]\n \"\"\"\n ",
"__typename": "CodeSnippetNode"
},
{
"lang": "Python3",
"langSlug": "python3",
"code": "class Solution:\n def countBits(self, n: int) -> List[int]:\n ",
"__typename": "CodeSnippetNode"
},
{
"lang": "C",
"langSlug": "c",
"code": "\n\n/**\n * Note: The returned array must be malloced, assume caller calls free().\n */\nint* countBits(int n, int* returnSize){\n\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "C#",
"langSlug": "csharp",
"code": "public class Solution {\n public int[] CountBits(int n) {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "JavaScript",
"langSlug": "javascript",
"code": "/**\n * @param {number} n\n * @return {number[]}\n */\nvar countBits = function(n) {\n \n};",
"__typename": "CodeSnippetNode"
},
{
"lang": "Ruby",
"langSlug": "ruby",
"code": "# @param {Integer} n\n# @return {Integer[]}\ndef count_bits(n)\n \nend",
"__typename": "CodeSnippetNode"
},
{
"lang": "Swift",
"langSlug": "swift",
"code": "class Solution {\n func countBits(_ n: Int) -> [Int] {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Go",
"langSlug": "golang",
"code": "func countBits(n int) []int {\n \n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Scala",
"langSlug": "scala",
"code": "object Solution {\n def countBits(n: Int): Array[Int] = {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Kotlin",
"langSlug": "kotlin",
"code": "class Solution {\n fun countBits(n: Int): IntArray {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "Rust",
"langSlug": "rust",
"code": "impl Solution {\n pub fn count_bits(n: i32) -> Vec<i32> {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "PHP",
"langSlug": "php",
"code": "class Solution {\n\n /**\n * @param Integer $n\n * @return Integer[]\n */\n function countBits($n) {\n \n }\n}",
"__typename": "CodeSnippetNode"
},
{
"lang": "TypeScript",
"langSlug": "typescript",
"code": "function countBits(n: number): number[] {\n\n};",
"__typename": "CodeSnippetNode"
},
{
"lang": "Racket",
"langSlug": "racket",
"code": "(define/contract (count-bits n)\n (-> exact-integer? (listof exact-integer?))\n\n )",
"__typename": "CodeSnippetNode"
},
{
"lang": "Erlang",
"langSlug": "erlang",
"code": "-spec count_bits(N :: integer()) -> [integer()].\ncount_bits(N) ->\n .",
"__typename": "CodeSnippetNode"
},
{
"lang": "Elixir",
"langSlug": "elixir",
"code": "defmodule Solution do\n @spec count_bits(n :: integer) :: [integer]\n def count_bits(n) do\n\n end\nend",
"__typename": "CodeSnippetNode"
}
],
"stats": "{\"totalAccepted\": \"552.3K\", \"totalSubmission\": \"745.4K\", \"totalAcceptedRaw\": 552287, \"totalSubmissionRaw\": 745372, \"acRate\": \"74.1%\"}",
"hints": [
"You should make use of what you have produced already.",
"Divide the numbers in ranges like [2-3], [4-7], [8-15] and so on. And try to generate new range from previous.",
"Or does the odd/even status of the number help you in calculating the number of 1s?"
],
"solution": {
"id": "73",
"canSeeDetail": false,
"paidOnly": true,
"hasVideoSolution": false,
"paidOnlyVideo": true,
"__typename": "ArticleNode"
},
"status": null,
"sampleTestCase": "2",
"metaData": "{\n \"name\": \"countBits\",\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": {
"id": "829",
"date": "2022-03-01",
"incompleteChallengeCount": 0,
"streakCount": 0,
"type": "DAILY",
"__typename": "ChallengeQuestionNode"
},
"__typename": "QuestionNode"
}
}
}