leetcode：641. 设计循环双端队列

设计循环双端队列
实现 MyCircularDeque 类:

MyCircularDeque(int k) ：构造函数,双端队列最大为 k 。
boolean insertFront()：将一个元素添加到双端队列头部。如果操作成功返回 true ，否则返回 false 。
boolean insertLast() ：将一个元素添加到双端队列尾部。如果操作成功返回 true ，否则返回 false 。
boolean deleteFront() ：从双端队列头部删除一个元素。如果操作成功返回 true ，否则返回 false 。
boolean deleteLast() ：从双端队列尾部删除一个元素。如果操作成功返回 true ，否则返回 false 。
int getFront() )：从双端队列头部获得一个元素。如果双端队列为空，返回 -1 。
int getRear() ：获得双端队列的最后一个元素。如果双端队列为空，返回 -1 。
boolean isEmpty() ：若双端队列为空，则返回 true ，否则返回 false 。
boolean isFull() ：若双端队列满了，则返回 true ，否则返回 false 。

示例 1：

输入
[“MyCircularDeque”, “insertLast”, “insertLast”, “insertFront”, “insertFront”, “getRear”, “isFull”, “deleteLast”, “insertFront”, “getFront”]
[[3], [1], [2], [3], [4], [], [], [], [4], []]
输出
[null, true, true, true, false, 2, true, true, true, 4]

解释
MyCircularDeque circularDeque = new MycircularDeque(3); // 设置容量大小为3
circularDeque.insertLast(1); // 返回 true
circularDeque.insertLast(2); // 返回 true
circularDeque.insertFront(3); // 返回 true
circularDeque.insertFront(4); // 已经满了，返回 false
circularDeque.getRear(); // 返回 2
circularDeque.isFull(); // 返回 true
circularDeque.deleteLast(); // 返回 true
circularDeque.insertFront(4); // 返回 true
circularDeque.getFront(); // 返回 4

提示：

1 <= k <= 1000
0 <= value <= 1000
insertFront, insertLast, deleteFront, deleteLast, getFront, getRear, isEmpty, isFull 调用次数不大于 2000 次

方法一：数组

class MyCircularDeque {
private:vector<int> elements;int rear, front;int capacity;public:MyCircularDeque(int k) {capacity = k + 1;rear = front = 0;elements = vector<int>(k + 1);}bool insertFront(int value) {if (isFull()) {return false;}front = (front - 1 + capacity) % capacity;elements[front] = value;return true;}bool insertLast(int value) {if (isFull()) {return false;}elements[rear] = value;rear = (rear + 1) % capacity;return true;}bool deleteFront() {if (isEmpty()) {return false;}front = (front + 1) % capacity;return true;}bool deleteLast() {if (isEmpty()) {return false;}rear = (rear - 1 + capacity) % capacity;return true;}int getFront() {if (isEmpty()) {return -1;}return elements[front];}int getRear() {if (isEmpty()) {return -1;}return elements[(rear - 1 + capacity) % capacity];}   bool isEmpty() {return rear == front;}bool isFull() {return (rear + 1) % capacity == front;}
};/*** Your MyCircularDeque object will be instantiated and called as such:* MyCircularDeque* obj = new MyCircularDeque(k);* bool param_1 = obj->insertFront(value);* bool param_2 = obj->insertLast(value);* bool param_3 = obj->deleteFront();* bool param_4 = obj->deleteLast();* int param_5 = obj->getFront();* int param_6 = obj->getRear();* bool param_7 = obj->isEmpty();* bool param_8 = obj->isFull();*/

方法二：链表

struct DLinkListNode {int val;DLinkListNode *prev, *next;DLinkListNode(int _val): val(_val), prev(nullptr), next(nullptr) {}
};class MyCircularDeque {
private:DLinkListNode *head, *tail;int capacity;int size;public:MyCircularDeque(int k): capacity(k), size(0), head(nullptr), tail(nullptr) {}bool insertFront(int value) {if (size == capacity) {return false;}DLinkListNode *node = new DLinkListNode(value);if (size == 0) {head = tail = node;} else {node->next = head;head->prev = node;head = node;}size++;return true;}bool insertLast(int value) {if (size == capacity) {return false;}DLinkListNode *node = new DLinkListNode(value);if (size == 0) {head = tail = node;} else {tail->next = node;node->prev = tail;tail = node;}size++;return true;}bool deleteFront() {if (size == 0) {return false;}DLinkListNode *node = head;head = head->next;if (head) {head->prev = nullptr;}delete node;size--;return true;}bool deleteLast() {if (size == 0) {return false;}DLinkListNode *node = tail;tail = tail->prev;if (tail) {tail->next = nullptr;}delete node;size--;return true;}int getFront() {if (size == 0) {return -1;}return head->val;}int getRear() {if (size == 0) {return -1;}return tail->val;}bool isEmpty() {return size == 0;}bool isFull() {return size == capacity;}
};/*** Your MyCircularDeque object will be instantiated and called as such:* MyCircularDeque* obj = new MyCircularDeque(k);* bool param_1 = obj->insertFront(value);* bool param_2 = obj->insertLast(value);* bool param_3 = obj->deleteFront();* bool param_4 = obj->deleteLast();* int param_5 = obj->getFront();* int param_6 = obj->getRear();* bool param_7 = obj->isEmpty();* bool param_8 = obj->isFull();*/