leetcode：641. 设计循环双端队列

641. 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();
 */