"content":"<p>Design a queue that supports <code>push</code> and <code>pop</code> operations in the front, middle, and back.</p>\n\n<p>Implement the <code>FrontMiddleBack</code> class:</p>\n\n<ul>\n\t<li><code>FrontMiddleBack()</code> Initializes the queue.</li>\n\t<li><code>void pushFront(int val)</code> Adds <code>val</code> to the <strong>front</strong> of the queue.</li>\n\t<li><code>void pushMiddle(int val)</code> Adds <code>val</code> to the <strong>middle</strong> of the queue.</li>\n\t<li><code>void pushBack(int val)</code> Adds <code>val</code> to the <strong>back</strong> of the queue.</li>\n\t<li><code>int popFront()</code> Removes the <strong>front</strong> element of the queue and returns it. If the queue is empty, return <code>-1</code>.</li>\n\t<li><code>int popMiddle()</code> Removes the <strong>middle</strong> element of the queue and returns it. If the queue is empty, return <code>-1</code>.</li>\n\t<li><code>int popBack()</code> Removes the <strong>back</strong> element of the queue and returns it. If the queue is empty, return <code>-1</code>.</li>\n</ul>\n\n<p><strong>Notice</strong> that when there are <b>two</b> middle position choices, the operation is performed on the <strong>frontmost</strong> middle position choice. For example:</p>\n\n<ul>\n\t<li>Pushing <code>6</code> into the middle of <code>[1, 2, 3, 4, 5]</code> results in <code>[1, 2, <u>6</u>, 3, 4, 5]</code>.</li>\n\t<li>Popping the middle from <code>[1, 2, <u>3</u>, 4, 5, 6]</code> returns <code>3</code> and results in <code>[1, 2, 4, 5, 6]</code>.</li>\n</ul>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong>\n["FrontMiddleBackQueue", "pushFront", "pushBack", "pushMiddle", "pushMiddle", "popFront", "popMiddle", "popMiddle", "popBack", "popFront"]\n[[], [1], [2], [3], [4], [], [], [], [], []]\n<strong>Output:</strong>\n[null, null, null, null, null, 1, 3, 4, 2, -1]\n\n<strong>Explanation:</strong>\nFrontMiddleBackQueue q = new FrontMiddleBackQueue();\nq.pushFront(1); // [<u>1</u>]\nq.pushBack(2); // [1, <u>2</u>]\nq.pushMiddle(3); // [1, <u>3</u>, 2]\nq.pushMiddle(4); // [1, <u>4</u>, 3, 2]\nq.popFront(); // return 1 -> [4, 3, 2]\nq.popMiddle(); // return 3 -> [4, 2]\nq.popMiddle(); // return 4 -> [2]\nq.popBack(); // return 2 -> []\nq.popFront(); // return -1 -> [] (The queue is empty)\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= val <= 10<sup>9</sup></code></li>\n\t<li>At most <code>1000</code> calls will be made to <code>pushFront</code>, <code>pushMiddle</code>, <code>pushBack</code>, <code>popFront</code>, <code>popMiddle</code>, and <code>popBack</code>.</li>\n</ul>\n",
"code":"class FrontMiddleBackQueue {\npublic:\n FrontMiddleBackQueue() {\n \n }\n \n void pushFront(int val) {\n \n }\n \n void pushMiddle(int val) {\n \n }\n \n void pushBack(int val) {\n \n }\n \n int popFront() {\n \n }\n \n int popMiddle() {\n \n }\n \n int popBack() {\n \n }\n};\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * FrontMiddleBackQueue* obj = new FrontMiddleBackQueue();\n * obj->pushFront(val);\n * obj->pushMiddle(val);\n * obj->pushBack(val);\n * int param_4 = obj->popFront();\n * int param_5 = obj->popMiddle();\n * int param_6 = obj->popBack();\n */",
"__typename":"CodeSnippetNode"
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{
"lang":"Java",
"langSlug":"java",
"code":"class FrontMiddleBackQueue {\n\n public FrontMiddleBackQueue() {\n \n }\n \n public void pushFront(int val) {\n \n }\n \n public void pushMiddle(int val) {\n \n }\n \n public void pushBack(int val) {\n \n }\n \n public int popFront() {\n \n }\n \n public int popMiddle() {\n \n }\n \n public int popBack() {\n \n }\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * FrontMiddleBackQueue obj = new FrontMiddleBackQueue();\n * obj.pushFront(val);\n * obj.pushMiddle(val);\n * obj.pushBack(val);\n * int param_4 = obj.popFront();\n * int param_5 = obj.popMiddle();\n * int param_6 = obj.popBack();\n */",
"code":"\n\n\ntypedef struct {\n \n} FrontMiddleBackQueue;\n\n\nFrontMiddleBackQueue* frontMiddleBackQueueCreate() {\n \n}\n\nvoid frontMiddleBackQueuePushFront(FrontMiddleBackQueue* obj, int val) {\n \n}\n\nvoid frontMiddleBackQueuePushMiddle(FrontMiddleBackQueue* obj, int val) {\n \n}\n\nvoid frontMiddleBackQueuePushBack(FrontMiddleBackQueue* obj, int val) {\n \n}\n\nint frontMiddleBackQueuePopFront(FrontMiddleBackQueue* obj) {\n \n}\n\nint frontMiddleBackQueuePopMiddle(FrontMiddleBackQueue* obj) {\n \n}\n\nint frontMiddleBackQueuePopBack(FrontMiddleBackQueue* obj) {\n \n}\n\nvoid frontMiddleBackQueueFree(FrontMiddleBackQueue* obj) {\n \n}\n\n/**\n * Your FrontMiddleBackQueue struct will be instantiated and called as such:\n * FrontMiddleBackQueue* obj = frontMiddleBackQueueCreate();\n * frontMiddleBackQueuePushFront(obj, val);\n \n * frontMiddleBackQueuePushMiddle(obj, val);\n \n * frontMiddleBackQueuePushBack(obj, val);\n \n * int param_4 = frontMiddleBackQueuePopFront(obj);\n \n * int param_5 = frontMiddleBackQueuePopMiddle(obj);\n \n * int param_6 = frontMiddleBackQueuePopBack(obj);\n \n * frontMiddleBackQueueFree(obj);\n*/",
"__typename":"CodeSnippetNode"
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{
"lang":"C#",
"langSlug":"csharp",
"code":"public class FrontMiddleBackQueue {\n\n public FrontMiddleBackQueue() {\n \n }\n \n public void PushFront(int val) {\n \n }\n \n public void PushMiddle(int val) {\n \n }\n \n public void PushBack(int val) {\n \n }\n \n public int PopFront() {\n \n }\n \n public int PopMiddle() {\n \n }\n \n public int PopBack() {\n \n }\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * FrontMiddleBackQueue obj = new FrontMiddleBackQueue();\n * obj.PushFront(val);\n * obj.PushMiddle(val);\n * obj.PushBack(val);\n * int param_4 = obj.PopFront();\n * int param_5 = obj.PopMiddle();\n * int param_6 = obj.PopBack();\n */",
"__typename":"CodeSnippetNode"
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"lang":"JavaScript",
"langSlug":"javascript",
"code":"\nvar FrontMiddleBackQueue = function() {\n \n};\n\n/** \n * @param {number} val\n * @return {void}\n */\nFrontMiddleBackQueue.prototype.pushFront = function(val) {\n \n};\n\n/** \n * @param {number} val\n * @return {void}\n */\nFrontMiddleBackQueue.prototype.pushMiddle = function(val) {\n \n};\n\n/** \n * @param {number} val\n * @return {void}\n */\nFrontMiddleBackQueue.prototype.pushBack = function(val) {\n \n};\n\n/**\n * @return {number}\n */\nFrontMiddleBackQueue.prototype.popFront = function() {\n \n};\n\n/**\n * @return {number}\n */\nFrontMiddleBackQueue.prototype.popMiddle = function() {\n \n};\n\n/**\n * @return {number}\n */\nFrontMiddleBackQueue.prototype.popBack = function() {\n \n};\n\n/** \n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * var obj = new FrontMiddleBackQueue()\n * obj.pushFront(val)\n * obj.pushMiddle(val)\n * obj.pushBack(val)\n * var param_4 = obj.popFront()\n * var param_5 = obj.popMiddle()\n * var param_6 = obj.popBack()\n */",
"code":"\nclass FrontMiddleBackQueue {\n\n init() {\n \n }\n \n func pushFront(_ val: Int) {\n \n }\n \n func pushMiddle(_ val: Int) {\n \n }\n \n func pushBack(_ val: Int) {\n \n }\n \n func popFront() -> Int {\n \n }\n \n func popMiddle() -> Int {\n \n }\n \n func popBack() -> Int {\n \n }\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * let obj = FrontMiddleBackQueue()\n * obj.pushFront(val)\n * obj.pushMiddle(val)\n * obj.pushBack(val)\n * let ret_4: Int = obj.popFront()\n * let ret_5: Int = obj.popMiddle()\n * let ret_6: Int = obj.popBack()\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Go",
"langSlug":"golang",
"code":"type FrontMiddleBackQueue struct {\n \n}\n\n\nfunc Constructor() FrontMiddleBackQueue {\n \n}\n\n\nfunc (this *FrontMiddleBackQueue) PushFront(val int) {\n \n}\n\n\nfunc (this *FrontMiddleBackQueue) PushMiddle(val int) {\n \n}\n\n\nfunc (this *FrontMiddleBackQueue) PushBack(val int) {\n \n}\n\n\nfunc (this *FrontMiddleBackQueue) PopFront() int {\n \n}\n\n\nfunc (this *FrontMiddleBackQueue) PopMiddle() int {\n \n}\n\n\nfunc (this *FrontMiddleBackQueue) PopBack() int {\n \n}\n\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * obj := Constructor();\n * obj.PushFront(val);\n * obj.PushMiddle(val);\n * obj.PushBack(val);\n * param_4 := obj.PopFront();\n * param_5 := obj.PopMiddle();\n * param_6 := obj.PopBack();\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Scala",
"langSlug":"scala",
"code":"class FrontMiddleBackQueue() {\n\n def pushFront(`val`: Int) {\n \n }\n\n def pushMiddle(`val`: Int) {\n \n }\n\n def pushBack(`val`: Int) {\n \n }\n\n def popFront(): Int = {\n \n }\n\n def popMiddle(): Int = {\n \n }\n\n def popBack(): Int = {\n \n }\n\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * var obj = new FrontMiddleBackQueue()\n * obj.pushFront(`val`)\n * obj.pushMiddle(`val`)\n * obj.pushBack(`val`)\n * var param_4 = obj.popFront()\n * var param_5 = obj.popMiddle()\n * var param_6 = obj.popBack()\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Kotlin",
"langSlug":"kotlin",
"code":"class FrontMiddleBackQueue() {\n\n fun pushFront(`val`: Int) {\n \n }\n\n fun pushMiddle(`val`: Int) {\n \n }\n\n fun pushBack(`val`: Int) {\n \n }\n\n fun popFront(): Int {\n \n }\n\n fun popMiddle(): Int {\n \n }\n\n fun popBack(): Int {\n \n }\n\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * var obj = FrontMiddleBackQueue()\n * obj.pushFront(`val`)\n * obj.pushMiddle(`val`)\n * obj.pushBack(`val`)\n * var param_4 = obj.popFront()\n * var param_5 = obj.popMiddle()\n * var param_6 = obj.popBack()\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"Rust",
"langSlug":"rust",
"code":"struct FrontMiddleBackQueue {\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 FrontMiddleBackQueue {\n\n fn new() -> Self {\n \n }\n \n fn push_front(&self, val: i32) {\n \n }\n \n fn push_middle(&self, val: i32) {\n \n }\n \n fn push_back(&self, val: i32) {\n \n }\n \n fn pop_front(&self) -> i32 {\n \n }\n \n fn pop_middle(&self) -> i32 {\n \n }\n \n fn pop_back(&self) -> i32 {\n \n }\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * let obj = FrontMiddleBackQueue::new();\n * obj.push_front(val);\n * obj.push_middle(val);\n * obj.push_back(val);\n * let ret_4: i32 = obj.pop_front();\n * let ret_5: i32 = obj.pop_middle();\n * let ret_6: i32 = obj.pop_back();\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"PHP",
"langSlug":"php",
"code":"class FrontMiddleBackQueue {\n /**\n */\n function __construct() {\n \n }\n \n /**\n * @param Integer $val\n * @return NULL\n */\n function pushFront($val) {\n \n }\n \n /**\n * @param Integer $val\n * @return NULL\n */\n function pushMiddle($val) {\n \n }\n \n /**\n * @param Integer $val\n * @return NULL\n */\n function pushBack($val) {\n \n }\n \n /**\n * @return Integer\n */\n function popFront() {\n \n }\n \n /**\n * @return Integer\n */\n function popMiddle() {\n \n }\n \n /**\n * @return Integer\n */\n function popBack() {\n \n }\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * $obj = FrontMiddleBackQueue();\n * $obj->pushFront($val);\n * $obj->pushMiddle($val);\n * $obj->pushBack($val);\n * $ret_4 = $obj->popFront();\n * $ret_5 = $obj->popMiddle();\n * $ret_6 = $obj->popBack();\n */",
"__typename":"CodeSnippetNode"
},
{
"lang":"TypeScript",
"langSlug":"typescript",
"code":"class FrontMiddleBackQueue {\n constructor() {\n\n }\n\n pushFront(val: number): void {\n\n }\n\n pushMiddle(val: number): void {\n\n }\n\n pushBack(val: number): void {\n\n }\n\n popFront(): number {\n\n }\n\n popMiddle(): number {\n\n }\n\n popBack(): number {\n\n }\n}\n\n/**\n * Your FrontMiddleBackQueue object will be instantiated and called as such:\n * var obj = new FrontMiddleBackQueue()\n * obj.pushFront(val)\n * obj.pushMiddle(val)\n * obj.pushBack(val)\n * var param_4 = obj.popFront()\n * var param_5 = obj.popMiddle()\n * var param_6 = obj.popBack()\n */",
"code":"-spec front_middle_back_queue_init_() -> any().\nfront_middle_back_queue_init_() ->\n .\n\n-spec front_middle_back_queue_push_front(Val :: integer()) -> any().\nfront_middle_back_queue_push_front(Val) ->\n .\n\n-spec front_middle_back_queue_push_middle(Val :: integer()) -> any().\nfront_middle_back_queue_push_middle(Val) ->\n .\n\n-spec front_middle_back_queue_push_back(Val :: integer()) -> any().\nfront_middle_back_queue_push_back(Val) ->\n .\n\n-spec front_middle_back_queue_pop_front() -> integer().\nfront_middle_back_queue_pop_front() ->\n .\n\n-spec front_middle_back_queue_pop_middle() -> integer().\nfront_middle_back_queue_pop_middle() ->\n .\n\n-spec front_middle_back_queue_pop_back() -> integer().\nfront_middle_back_queue_pop_back() ->\n .\n\n\n%% Your functions will be called as such:\n%% front_middle_back_queue_init_(),\n%% front_middle_back_queue_push_front(Val),\n%% front_middle_back_queue_push_middle(Val),\n%% front_middle_back_queue_push_back(Val),\n%% Param_4 = front_middle_back_queue_pop_front(),\n%% Param_5 = front_middle_back_queue_pop_middle(),\n%% Param_6 = front_middle_back_queue_pop_back(),\n\n%% front_middle_back_queue_init_ will be called before every test case, in which you can do some necessary initializations.",
"__typename":"CodeSnippetNode"
},
{
"lang":"Elixir",
"langSlug":"elixir",
"code":"defmodule FrontMiddleBackQueue do\n @spec init_() :: any\n def init_() do\n\n end\n\n @spec push_front(val :: integer) :: any\n def push_front(val) do\n\n end\n\n @spec push_middle(val :: integer) :: any\n def push_middle(val) do\n\n end\n\n @spec push_back(val :: integer) :: any\n def push_back(val) do\n\n end\n\n @spec pop_front() :: integer\n def pop_front() do\n\n end\n\n @spec pop_middle() :: integer\n def pop_middle() do\n\n end\n\n @spec pop_back() :: integer\n def pop_back() do\n\n end\nend\n\n# Your functions will be called as such:\n# FrontMiddleBackQueue.init_()\n# FrontMiddleBackQueue.push_front(val)\n# FrontMiddleBackQueue.push_middle(val)\n# FrontMiddleBackQueue.push_back(val)\n# param_4 = FrontMiddleBackQueue.pop_front()\n# param_5 = FrontMiddleBackQueue.pop_middle()\n# param_6 = FrontMiddleBackQueue.pop_back()\n\n# FrontMiddleBackQueue.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++ 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:
