622. Design Circular Queue

Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle and the last position is connected back to the first position to make a circle. It is also called "Ring Buffer".

One of the benefits of the circular queue is that we can make use of the spaces in front of the queue. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.

Your implementation should support following operations:

• MyCircularQueue(k): Constructor, set the size of the queue to be k.

• Front: Get the front item from the queue. If the queue is empty, return -1.

• Rear: Get the last item from the queue. If the queue is empty, return -1.

• enQueue(value): Insert an element into the circular queue. Return true if the operation is successful.

• deQueue(): Delete an element from the circular queue. Return true if the operation is successful.

• isEmpty(): Checks whether the circular queue is empty or not.

• isFull(): Checks whether the circular queue is full or not.

Example:

MyCircularQueue circularQueue = new MyCircularQueue(3); // set the size to be 3
circularQueue.enQueue(1);  // return true
circularQueue.enQueue(2);  // return true
circularQueue.enQueue(3);  // return true
circularQueue.enQueue(4);  // return false, the queue is full
circularQueue.Rear();  // return 3
circularQueue.isFull();  // return true
circularQueue.deQueue();  // return true
circularQueue.enQueue(4);  // return true
circularQueue.Rear();  // return 4

Note:

• All values will be in the range of [0, 1000].

• The number of operations will be in the range of [1, 1000].

• Please do not use the built-in Queue library.

class MyCircularQueue {
public:
    /** Initialize your data structure here. Set the size of the queue to be k. */
    MyCircularQueue(int k) : /*data(vector<int>(k)), */front(0), rear(-1), cnt(0), sz(k) {
        data = new int[k];
    }
    ~MyCircularQueue() {
        delete[] data;
    }
    /** Insert an element into the circular queue. Return true if the operation is successful. */
    bool enQueue(int value) {
        if (isFull()) return false;
        // rear = (rear + 1) % data.size();
        rear = (rear + 1) % sz;
        data[rear] = value;
        ++cnt;
        return true;
    }
    
    /** Delete an element from the circular queue. Return true if the operation is successful. */
    bool deQueue() {
        if (isEmpty()) return false;
        // front = (front + 1) % data.size();
        front = (front + 1) % sz;
        --cnt;
        return true;
    }
    
    /** Get the front item from the queue. */
    int Front() {
        return isEmpty() ? -1 : data[front];
    }
    
    /** Get the last item from the queue. */
    int Rear() {
        return isEmpty() ? -1 : data[rear];
    }
    
    /** Checks whether the circular queue is empty or not. */
    bool isEmpty() {
        return cnt == 0;
    }
    
    /** Checks whether the circular queue is full or not. */
    bool isFull() {
        // return cnt == data.size();
        return cnt == sz;
    }
private:
    // vector<int> data;
    int* data;
    int front, rear, cnt, sz;
};