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"data": {
"question": {
"questionId": "1767",
"questionFrontendId": "1670",
"categoryTitle": "Algorithms",
"boundTopicId": 499831,
"title": "Design Front Middle Back Queue",
"titleSlug": "design-front-middle-back-queue",
"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 class=\"example\">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",
"translatedTitle": "设计前中后队列",
"translatedContent": "<p>请你设计一个队列，支持在前，中，后三个位置的 <code>push</code> 和 <code>pop</code> 操作。</p>\n\n<p>请你完成 <code>FrontMiddleBack</code> 类：</p>\n\n<ul>\n\t<li><code>FrontMiddleBack()</code> 初始化队列。</li>\n\t<li><code>void pushFront(int val)</code> 将 <code>val</code> 添加到队列的 <strong>最前面</strong> 。</li>\n\t<li><code>void pushMiddle(int val)</code> 将 <code>val</code> 添加到队列的 <strong>正中间</strong> 。</li>\n\t<li><code>void pushBack(int val)</code> 将 <code>val</code> 添加到队里的 <strong>最后面</strong> 。</li>\n\t<li><code>int popFront()</code> 将 <strong>最前面</strong> 的元素从队列中删除并返回值，如果删除之前队列为空，那么返回 <code>-1</code> 。</li>\n\t<li><code>int popMiddle()</code> 将 <b>正中间</b> 的元素从队列中删除并返回值，如果删除之前队列为空，那么返回 <code>-1</code> 。</li>\n\t<li><code>int popBack()</code> 将 <strong>最后面</strong> 的元素从队列中删除并返回值，如果删除之前队列为空，那么返回 <code>-1</code> 。</li>\n</ul>\n\n<p>请注意当有 <strong>两个</strong> 中间位置的时候，选择靠前面的位置进行操作。比方说：</p>\n\n<ul>\n\t<li>将 <code>6</code> 添加到 <code>[1, 2, 3, 4, 5]</code> 的中间位置，结果数组为 <code>[1, 2, <strong>6</strong>, 3, 4, 5]</code> 。</li>\n\t<li>从 <code>[1, 2, <strong>3</strong>, 4, 5, 6]</code> 的中间位置弹出元素，返回 <code>3</code> ，数组变为 <code>[1, 2, 4, 5, 6]</code> 。</li>\n</ul>\n\n<p> </p>\n\n<p><strong>示例 1：</strong></p>\n\n<pre>\n<strong>输入：</strong>\n[\"FrontMiddleBackQueue\", \"pushFront\", \"pushBack\", \"pushMiddle\", \"pushMiddle\", \"popFront\", \"popMiddle\", \"popMiddle\", \"popBack\", \"popFront\"]\n[[], [1], [2], [3], [4], [], [], [], [], []]\n<strong>输出：</strong>\n[null, null, null, null, null, 1, 3, 4, 2, -1]\n\n<strong>解释：</strong>\nFrontMiddleBackQueue q = new FrontMiddleBackQueue();\nq.pushFront(1); // [<strong>1</strong>]\nq.pushBack(2); // [1, <strong>2</strong>]\nq.pushMiddle(3); // [1, <strong>3</strong>, 2]\nq.pushMiddle(4); // [1, <strong>4</strong>, 3, 2]\nq.popFront(); // 返回 1 -> [4, 3, 2]\nq.popMiddle(); // 返回 3 -> [4, 2]\nq.popMiddle(); // 返回 4 -> [2]\nq.popBack(); // 返回 2 -> []\nq.popFront(); // 返回 -1 -> [] （队列为空）\n</pre>\n\n<p> </p>\n\n<p><strong>提示：</strong></p>\n\n<ul>\n\t<li><code>1 <= val <= 10<sup>9</sup></code></li>\n\t<li>最多调用 <code>1000</code> 次 <code>pushFront</code>， <code>pushMiddle</code>， <code>pushBack</code>， <code>popFront</code>， <code>popMiddle</code> 和 <code>popBack</code> 。</li>\n</ul>\n",
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{
"lang": "C++",
"langSlug": "cpp",
"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 */",
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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 */",
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"lang": "Python",
"langSlug": "python",
"code": "class FrontMiddleBackQueue(object):\n\n def __init__(self):\n\n\n def pushFront(self, val):\n \"\"\"\n :type val: int\n :rtype: None\n \"\"\"\n\n\n def pushMiddle(self, val):\n \"\"\"\n :type val: int\n :rtype: None\n \"\"\"\n\n\n def pushBack(self, val):\n \"\"\"\n :type val: int\n :rtype: None\n \"\"\"\n\n\n def popFront(self):\n \"\"\"\n :rtype: int\n \"\"\"\n\n\n def popMiddle(self):\n \"\"\"\n :rtype: int\n \"\"\"\n\n\n def popBack(self):\n \"\"\"\n :rtype: int\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# param_4 = obj.popFront()\n# param_5 = obj.popMiddle()\n# param_6 = obj.popBack()",
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"lang": "Python3",
"langSlug": "python3",
"code": "class FrontMiddleBackQueue:\n\n def __init__(self):\n\n\n def pushFront(self, val: int) -> None:\n\n\n def pushMiddle(self, val: int) -> None:\n\n\n def pushBack(self, val: int) -> None:\n\n\n def popFront(self) -> int:\n\n\n def popMiddle(self) -> int:\n\n\n def popBack(self) -> int:\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# param_4 = obj.popFront()\n# param_5 = obj.popMiddle()\n# param_6 = obj.popBack()",
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"lang": "C",
"langSlug": "c",
"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*/",
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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 */",
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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 */",
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"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 */",
"__typename": "CodeSnippetNode"
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"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 */",
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"lang": "Swift",
"langSlug": "swift",
"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": "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"
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{
"lang": "Dart",
"langSlug": "dart",
"code": "class FrontMiddleBackQueue {\n\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 = FrontMiddleBackQueue();\n * obj.pushFront(val);\n * obj.pushMiddle(val);\n * obj.pushBack(val);\n * int param4 = obj.popFront();\n * int param5 = obj.popMiddle();\n * int param6 = obj.popBack();\n */",
"__typename": "CodeSnippetNode"
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{
"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 */",
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{
"lang": "Ruby",
"langSlug": "ruby",
"code": "class FrontMiddleBackQueue\n def initialize()\n\n end\n\n\n=begin\n :type val: Integer\n :rtype: Void\n=end\n def push_front(val)\n\n end\n\n\n=begin\n :type val: Integer\n :rtype: Void\n=end\n def push_middle(val)\n\n end\n\n\n=begin\n :type val: Integer\n :rtype: Void\n=end\n def push_back(val)\n\n end\n\n\n=begin\n :rtype: Integer\n=end\n def pop_front()\n\n end\n\n\n=begin\n :rtype: Integer\n=end\n def pop_middle()\n\n end\n\n\n=begin\n :rtype: Integer\n=end\n def pop_back()\n\n end\n\n\nend\n\n# Your FrontMiddleBackQueue object will be instantiated and called as such:\n# obj = FrontMiddleBackQueue.new()\n# obj.push_front(val)\n# obj.push_middle(val)\n# obj.push_back(val)\n# param_4 = obj.pop_front()\n# param_5 = obj.pop_middle()\n# param_6 = obj.pop_back()",
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{
"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"
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{
"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 */",
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"lang": "Racket",
"langSlug": "racket",
"code": "(define front-middle-back-queue%\n (class object%\n (super-new)\n \n (init-field)\n \n ; push-front : exact-integer? -> void?\n (define/public (push-front val)\n )\n ; push-middle : exact-integer? -> void?\n (define/public (push-middle val)\n )\n ; push-back : exact-integer? -> void?\n (define/public (push-back val)\n )\n ; pop-front : -> exact-integer?\n (define/public (pop-front)\n )\n ; pop-middle : -> exact-integer?\n (define/public (pop-middle)\n )\n ; pop-back : -> exact-integer?\n (define/public (pop-back)\n )))\n\n;; Your front-middle-back-queue% object will be instantiated and called as such:\n;; (define obj (new front-middle-back-queue%))\n;; (send obj push-front val)\n;; (send obj push-middle val)\n;; (send obj push-back val)\n;; (define param_4 (send obj pop-front))\n;; (define param_5 (send obj pop-middle))\n;; (define param_6 (send obj pop-back))",
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"lang": "Erlang",
"langSlug": "erlang",
"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.",
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"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.",
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"hints": [
"The constraints are low enough for a brute force, single array approach.",
"For an O(1) per method approach, use 2 double-ended queues: one for the first half and one for the second half."
],
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