"content":"<p>Design and implement a data structure for a <a href=\"https://en.wikipedia.org/wiki/Least_frequently_used\" target=\"_blank\">Least Frequently Used (LFU)</a> cache.</p>\n\n<p>Implement the <code>LFUCache</code> class:</p>\n\n<ul>\n\t<li><code>LFUCache(int capacity)</code> Initializes the object with the <code>capacity</code> of the data structure.</li>\n\t<li><code>int get(int key)</code> Gets the value of the <code>key</code> if the <code>key</code> exists in the cache. Otherwise, returns <code>-1</code>.</li>\n\t<li><code>void put(int key, int value)</code> Update the value of the <code>key</code> if present, or inserts the <code>key</code> if not already present. When the cache reaches its <code>capacity</code>, it should invalidate and remove the <strong>least frequently used</strong> key before inserting a new item. For this problem, when there is a <strong>tie</strong> (i.e., two or more keys with the same frequency), the <strong>least recently used</strong> <code>key</code> would be invalidated.</li>\n</ul>\n\n<p>To determine the least frequently used key, a <strong>use counter</strong> is maintained for each key in the cache. The key with the smallest <strong>use counter</strong> is the least frequently used key.</p>\n\n<p>When a key is first inserted into the cache, its <strong>use counter</strong> is set to <code>1</code> (due to the <code>put</code> operation). The <strong>use counter</strong> for a key in the cache is incremented either a <code>get</code> or <code>put</code> operation is called on it.</p>\n\n<p>The functions <code data-stringify-type=\"code\">get</code> and <code data-stringify-type=\"code\">put</code> must each run in <code>O(1)</code> average time complexity.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input</strong>\n["LFUCache", "put", "put", "get", "put", "get", "get", "put", "get", "get", "get"]\n[[2], [1, 1], [2, 2], [1], [3, 3], [2], [3], [4, 4], [1], [3], [4]]\n<strong>Output</strong>\n[null, null, null, 1, null, -1, 3, null, -1, 3, 4]\n\n<strong>Explanation</strong>\n// cnt(x) = the use counter for key x\n// cache=[] will show the last used order for tiebreakers (leftmost element is most recent)\nLFUCache lfu = new LFUCache(2);\nlfu.put(1, 1); // cache=[1,_], cnt(1)=1\nlfu.put(2, 2); // cache=[2,1], cnt(2)=1, cnt(1)=1\nlfu.get(1); // return 1\n // cache=[1,2], cnt(2)=1, cnt(1)=2\nlfu.put(3, 3); // 2 is the LFU key because cnt(2)=1 is the smallest, invalidate 2.\n // cache=[3,1], cnt(3)=1, cnt(1)=2\nlfu.get(2); // return -1 (not found)\nlfu.get(3); // return 3\n // cache=[3,1], cnt(3)=2, cnt(1)=2\nlfu.put(4, 4); // Both 1 and 3 have the same cnt, but 1 is LRU, invalidate 1.\n // cache=[4,3], cnt(4)=1, cnt(3)=2\nlfu.get(1); // return -1 (not found)\nlfu.get(3); // return 3\n // cache=[3,4], cnt(4)=1, cnt(3)=3\nlfu.get(4); // return 4\n // cache=[4,3], cnt(4)=2, cnt(3)=3\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= capacity <= 10<sup>4</sup></code></li>\n\t<li><code>0 <= key <= 10<sup>5</sup></code></li>\n\t<li><code>0 <= value <= 10<sup>9</sup></code></li>\n\t<li>At most <code>2 * 10<sup>5</sup></code> calls will be made to <code>get</code> and <code>put</code>.</li>\n</ul>\n\n<p> </p>\n<span style=\"display: none;\"> </span>",
"code":"class LFUCache {\npublic:\n LFUCache(int capacity) {\n \n }\n \n int get(int key) {\n \n }\n \n void put(int key, int value) {\n \n }\n};\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * LFUCache* obj = new LFUCache(capacity);\n * int param_1 = obj->get(key);\n * obj->put(key,value);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Java",
"langSlug":"java",
"code":"class LFUCache {\n\n public LFUCache(int capacity) {\n \n }\n \n public int get(int key) {\n \n }\n \n public void put(int key, int value) {\n \n }\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * LFUCache obj = new LFUCache(capacity);\n * int param_1 = obj.get(key);\n * obj.put(key,value);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Python",
"langSlug":"python",
"code":"class LFUCache(object):\n\n def __init__(self, capacity):\n \"\"\"\n :type capacity: int\n \"\"\"\n \n\n def get(self, key):\n \"\"\"\n :type key: int\n :rtype: int\n \"\"\"\n \n\n def put(self, key, value):\n \"\"\"\n :type key: int\n :type value: int\n :rtype: None\n \"\"\"\n \n\n\n# Your LFUCache object will be instantiated and called as such:\n# obj = LFUCache(capacity)\n# param_1 = obj.get(key)\n# obj.put(key,value)",
"__typename":"CodeSnippetNode"
},
{
"lang":"Python3",
"langSlug":"python3",
"code":"class LFUCache:\n\n def __init__(self, capacity: int):\n \n\n def get(self, key: int) -> int:\n \n\n def put(self, key: int, value: int) -> None:\n \n\n\n# Your LFUCache object will be instantiated and called as such:\n# obj = LFUCache(capacity)\n# param_1 = obj.get(key)\n# obj.put(key,value)",
"code":"public class LFUCache {\n\n public LFUCache(int capacity) {\n \n }\n \n public int Get(int key) {\n \n }\n \n public void Put(int key, int value) {\n \n }\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * LFUCache obj = new LFUCache(capacity);\n * int param_1 = obj.Get(key);\n * obj.Put(key,value);\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"JavaScript",
"langSlug":"javascript",
"code":"/**\n * @param {number} capacity\n */\nvar LFUCache = function(capacity) {\n \n};\n\n/** \n * @param {number} key\n * @return {number}\n */\nLFUCache.prototype.get = function(key) {\n \n};\n\n/** \n * @param {number} key \n * @param {number} value\n * @return {void}\n */\nLFUCache.prototype.put = function(key, value) {\n \n};\n\n/** \n * Your LFUCache object will be instantiated and called as such:\n * var obj = new LFUCache(capacity)\n * var param_1 = obj.get(key)\n * obj.put(key,value)\n */",
"code":"class LFUCache {\n constructor(capacity: number) {\n \n }\n\n get(key: number): number {\n \n }\n\n put(key: number, value: number): void {\n \n }\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * var obj = new LFUCache(capacity)\n * var param_1 = obj.get(key)\n * obj.put(key,value)\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"PHP",
"langSlug":"php",
"code":"class LFUCache {\n /**\n * @param Integer $capacity\n */\n function __construct($capacity) {\n \n }\n \n /**\n * @param Integer $key\n * @return Integer\n */\n function get($key) {\n \n }\n \n /**\n * @param Integer $key\n * @param Integer $value\n * @return NULL\n */\n function put($key, $value) {\n \n }\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * $obj = LFUCache($capacity);\n * $ret_1 = $obj->get($key);\n * $obj->put($key, $value);\n */",
"code":"class LFUCache(capacity: Int) {\n\n fun get(key: Int): Int {\n \n }\n\n fun put(key: Int, value: Int) {\n \n }\n\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * var obj = LFUCache(capacity)\n * var param_1 = obj.get(key)\n * obj.put(key,value)\n */",
"code":"class LFUCache(_capacity: Int) {\n\n def get(key: Int): Int = {\n \n }\n\n def put(key: Int, value: Int) {\n \n }\n\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * var obj = new LFUCache(capacity)\n * var param_1 = obj.get(key)\n * obj.put(key,value)\n */",
"code":"struct LFUCache {\n\n}\n\n\n/** \n * `&self` means the method takes an immutable reference.\n * If you need a mutable reference, change it to `&mut self` instead.\n */\nimpl LFUCache {\n\n fn new(capacity: i32) -> Self {\n \n }\n \n fn get(&self, key: i32) -> i32 {\n \n }\n \n fn put(&self, key: i32, value: i32) {\n \n }\n}\n\n/**\n * Your LFUCache object will be instantiated and called as such:\n * let obj = LFUCache::new(capacity);\n * let ret_1: i32 = obj.get(key);\n * obj.put(key, value);\n */",
"code":"-spec lfu_cache_init_(Capacity :: integer()) -> any().\nlfu_cache_init_(Capacity) ->\n .\n\n-spec lfu_cache_get(Key :: integer()) -> integer().\nlfu_cache_get(Key) ->\n .\n\n-spec lfu_cache_put(Key :: integer(), Value :: integer()) -> any().\nlfu_cache_put(Key, Value) ->\n .\n\n\n%% Your functions will be called as such:\n%% lfu_cache_init_(Capacity),\n%% Param_1 = lfu_cache_get(Key),\n%% lfu_cache_put(Key, Value),\n\n%% lfu_cache_init_ will be called before every test case, in which you can do some necessary initializations.",
"code":"defmodule LFUCache do\n @spec init_(capacity :: integer) :: any\n def init_(capacity) do\n \n end\n\n @spec get(key :: integer) :: integer\n def get(key) do\n \n end\n\n @spec put(key :: integer, value :: integer) :: any\n def put(key, value) do\n \n end\nend\n\n# Your functions will be called as such:\n# LFUCache.init_(capacity)\n# param_1 = LFUCache.get(key)\n# LFUCache.put(key, value)\n\n# LFUCache.init_ will be called before every test case, in which you can do some necessary initializations.",
"envInfo":"{\"cpp\": [\"C++\", \"<p>Compiled with <code> clang 11 </code> using the latest C++ 20 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 gnu11 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://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-10\\\" target=\\\"_blank\\\">C# 10 with .NET 6 runtime</a></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 5.3.0 version of <a href=\\\"https://github.com/datastructures-js/priority-queue/tree/fb4fdb984834421279aeb081df7af624d17c2a03\\\" target=\\\"_blank\\\">datastructures-js/priority-queue</a> and 4.2.1 version of <a href=\\\"https://githu
