mirror of
https://gitee.com/coder-xiaomo/leetcode-problemset
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173 lines
17 KiB
JSON
173 lines
17 KiB
JSON
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"questionFrontendId": "753",
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"title": "Cracking the Safe",
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"titleSlug": "cracking-the-safe",
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"content": "<p>There is a safe protected by a password. The password is a sequence of <code>n</code> digits where each digit can be in the range <code>[0, k - 1]</code>.</p>\n\n<p>The safe has a peculiar way of checking the password. When you enter in a sequence, it checks the <strong>most recent </strong><code>n</code><strong> digits</strong> that were entered each time you type a digit.</p>\n\n<ul>\n\t<li>For example, the correct password is <code>"345"</code> and you enter in <code>"012345"</code>:\n\n\t<ul>\n\t\t<li>After typing <code>0</code>, the most recent <code>3</code> digits is <code>"0"</code>, which is incorrect.</li>\n\t\t<li>After typing <code>1</code>, the most recent <code>3</code> digits is <code>"01"</code>, which is incorrect.</li>\n\t\t<li>After typing <code>2</code>, the most recent <code>3</code> digits is <code>"012"</code>, which is incorrect.</li>\n\t\t<li>After typing <code>3</code>, the most recent <code>3</code> digits is <code>"123"</code>, which is incorrect.</li>\n\t\t<li>After typing <code>4</code>, the most recent <code>3</code> digits is <code>"234"</code>, which is incorrect.</li>\n\t\t<li>After typing <code>5</code>, the most recent <code>3</code> digits is <code>"345"</code>, which is correct and the safe unlocks.</li>\n\t</ul>\n\t</li>\n</ul>\n\n<p>Return <em>any string of <strong>minimum length</strong> that will unlock the safe <strong>at some point</strong> of entering it</em>.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 1, k = 2\n<strong>Output:</strong> "10"\n<strong>Explanation:</strong> The password is a single digit, so enter each digit. "01" would also unlock the safe.\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> n = 2, k = 2\n<strong>Output:</strong> "01100"\n<strong>Explanation:</strong> For each possible password:\n- "00" is typed in starting from the 4<sup>th</sup> digit.\n- "01" is typed in starting from the 1<sup>st</sup> digit.\n- "10" is typed in starting from the 3<sup>rd</sup> digit.\n- "11" is typed in starting from the 2<sup>nd</sup> digit.\nThus "01100" will unlock the safe. "01100", "10011", and "11001" would also unlock the safe.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= n <= 4</code></li>\n\t<li><code>1 <= k <= 10</code></li>\n\t<li><code>1 <= k<sup>n</sup> <= 4096</code></li>\n</ul>\n",
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"translatedContent": null,
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"isPaidOnly": false,
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"difficulty": "Hard",
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"likes": 183,
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"similarQuestions": "[]",
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"exampleTestcases": "1\n2\n2\n2",
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"categoryTitle": "Algorithms",
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"contributors": [],
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"topicTags": [
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"name": "Depth-First Search",
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"slug": "depth-first-search",
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"name": "Graph",
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"slug": "graph",
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"name": "Eulerian Circuit",
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"lang": "C++",
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"langSlug": "cpp",
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"code": "class Solution {\npublic:\n string crackSafe(int n, int k) {\n \n }\n};",
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"lang": "Java",
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"langSlug": "java",
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"code": "class Solution {\n public String crackSafe(int n, int k) {\n \n }\n}",
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"lang": "Python",
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"langSlug": "python",
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"code": "class Solution(object):\n def crackSafe(self, n, k):\n \"\"\"\n :type n: int\n :type k: int\n :rtype: str\n \"\"\"\n ",
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"lang": "Python3",
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"code": "class Solution:\n def crackSafe(self, n: int, k: int) -> str:\n ",
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"lang": "C",
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"code": "\n\nchar * crackSafe(int n, int k){\n\n}",
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"lang": "C#",
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"langSlug": "csharp",
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"code": "public class Solution {\n public string CrackSafe(int n, int k) {\n \n }\n}",
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"lang": "JavaScript",
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"code": "/**\n * @param {number} n\n * @param {number} k\n * @return {string}\n */\nvar crackSafe = function(n, k) {\n \n};",
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"lang": "Ruby",
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"langSlug": "ruby",
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"code": "# @param {Integer} n\n# @param {Integer} k\n# @return {String}\ndef crack_safe(n, k)\n \nend",
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"lang": "Swift",
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"langSlug": "swift",
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"code": "class Solution {\n func crackSafe(_ n: Int, _ k: Int) -> String {\n \n }\n}",
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"lang": "Go",
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"code": "func crackSafe(n int, k int) string {\n \n}",
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"lang": "Scala",
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"code": "object Solution {\n def crackSafe(n: Int, k: Int): String = {\n \n }\n}",
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"lang": "Kotlin",
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"code": "class Solution {\n fun crackSafe(n: Int, k: Int): String {\n \n }\n}",
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"lang": "Rust",
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"langSlug": "rust",
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"code": "impl Solution {\n pub fn crack_safe(n: i32, k: i32) -> String {\n \n }\n}",
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"lang": "PHP",
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"langSlug": "php",
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"code": "class Solution {\n\n /**\n * @param Integer $n\n * @param Integer $k\n * @return String\n */\n function crackSafe($n, $k) {\n \n }\n}",
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"langSlug": "typescript",
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"code": "function crackSafe(n: number, k: number): string {\n\n};",
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"code": "(define/contract (crack-safe n k)\n (-> exact-integer? exact-integer? string?)\n\n )",
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"code": "-spec crack_safe(N :: integer(), K :: integer()) -> unicode:unicode_binary().\ncrack_safe(N, K) ->\n .",
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"code": "defmodule Solution do\n @spec crack_safe(n :: integer, k :: integer) :: String.t\n def crack_safe(n, k) do\n\n end\nend",
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"hints": [
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"We can think of this problem as the problem of finding an Euler path (a path visiting every edge exactly once) on the following graph: there are $$k^{n-1}$$ nodes with each node having $$k$$ edges. It turns out this graph always has an Eulerian circuit (path starting where it ends.)\r\n\r\nWe should visit each node in \"post-order\" so as to not get stuck in the graph prematurely."
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"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:
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