力扣每日一题2022-08-15中等题：设计循环双端队列

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题目描述

设计循环双端队列

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思路

双数组模拟

可以利用循环队列实现双端队列，在循环队列的基础上，增加insertFront和deleteFront函数实现即可。队列具备如下几个属性：front（队首索引）、rear（队尾索引）、elements（一个固定大小的数组）、capacity（循环队列的容量）。根据题意，循环双端队列需要实现如下接口：

• MyCircularDeque(int k)：初始化队列，同时数组空间初始化大小为k+1，front和rear都初始化为0。
• insertFront(int value)：当队列未满时，在队首插入一个元素，将队首指针front移动一个位置，更新队首索引为(front-1+capacity) mod capacity。
• insertLast(int value)：当队列未满时，在队尾插入一个元素，将队尾指针rear更新为(rear+1) mod capacity。
• deleteFront()：当队列不为空时，从队首删除一个元素，并同时将队首的索引front更新为(front+1) mod capacity。
• deleteLast()：当队列不为空时，从队尾删除一个元素，并同时将队尾索引rear更新为(rear-1+capacity) mod capacity。
• getFront()：当队列非空，返回队首元素。
• getRear()：当队列非空，返回队尾元素。
• isEmpty()：判断队列是否为空，只需要判断rear和front是否相等。
• isFull()：判断队列是否已满，只需判断front是否等于(rear+1) mod capacity。

Python实现

class MyCircularDeque:

    def __init__(self, k: int):
        self.front = self.rear = 0
        self.elements = [0] * (k+1)


    def insertFront(self, value: int) -> bool:
        if self.isFull():
            return False
        self.front = (self.front - 1) % len(self.elements)
        self.elements[self.front] = value
        return True


    def insertLast(self, value: int) -> bool:
        if self.isFull():
            return False
        self.elements[self.rear] = value
        self.rear = (self.rear + 1) % len(self.elements)
        return True


    def deleteFront(self) -> bool:
        if self.isEmpty():
            return False
        self.front = (self.front + 1) % len(self.elements)
        return True


    def deleteLast(self) -> bool:
        if self.isEmpty():
            return False
        self.rear = (self.rear - 1) % len(self.elements)
        return True


    def getFront(self) -> int:
        return -1 if self.isEmpty() else self.elements[self.front]


    def getRear(self) -> int:
        return -1 if self.isEmpty() else self.elements[(self.rear - 1) % len(self.elements)]


    def isEmpty(self) -> bool:
        return self.front == self.rear


    def isFull(self) -> bool:
        return (self.rear + 1) % len(self.elements) == self.front



# Your MyCircularDeque object will be instantiated and called as such:
# obj = MyCircularDeque(k)
# param_1 = obj.insertFront(value)
# param_2 = obj.insertLast(value)
# param_3 = obj.deleteFront()
# param_4 = obj.deleteLast()
# param_5 = obj.getFront()
# param_6 = obj.getRear()
# param_7 = obj.isEmpty()
# param_8 = obj.isFull()

Java实现

class MyCircularDeque {

    private int[] elements;
    private int front, rear, capacity;

    public MyCircularDeque(int k) {
        capacity = k + 1;
        rear = front = 0;
        elements = new int[k+1];
    }
    
    public boolean insertFront(int value) {
        if (isFull()) {
            return false;
        }
        front = (front - 1 + capacity) % capacity;
        elements[front] = value;
        return true;
    }
    
    public boolean insertLast(int value) {
        if (isFull()) {
            return false;
        }
        elements[rear] = value;
        rear = (rear + 1) % capacity;
        return true;
    }
    
    public boolean deleteFront() {
        if (isEmpty()) {
            return false;
        }
        front = (front + 1) % capacity;
        return true;
    }
    
    public boolean deleteLast() {
        if (isEmpty()) {
            return false;
        }
        rear = (rear - 1 + capacity) % capacity;
        return true;
    }
    
    public int getFront() {
        if (isEmpty()) {
            return -1;
        }
        return elements[front];
    }
    
    public int getRear() {
        if (isEmpty()) {
            return -1;
        }
        return elements[(rear - 1 + capacity) % capacity];
    }
    
    public boolean isEmpty() {
        return front == rear;
    }
    
    public boolean isFull() {
        return (rear + 1) % capacity == front;
    }
}

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque obj = new MyCircularDeque(k);
 * boolean param_1 = obj.insertFront(value);
 * boolean param_2 = obj.insertLast(value);
 * boolean param_3 = obj.deleteFront();
 * boolean param_4 = obj.deleteLast();
 * int param_5 = obj.getFront();
 * int param_6 = obj.getRear();
 * boolean param_7 = obj.isEmpty();
 * boolean param_8 = obj.isFull();
 */

C++实现

class MyCircularDeque {
private:
    vector<int> elements;
    int front, rear, capacity;

public:
    MyCircularDeque(int k) {
        capacity = k+1;
        front = rear = 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 front == rear;
    }
    
    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();
 */