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

 1 class MyCircularQueue {
 2     final int[] a;
 3     int front, rear = -1, len = 0;
 4 
 5     public MyCircularQueue(int k) {
 6         a = new int[k];
 7     }
 8 
 9     public boolean enQueue(int val) {
10         if (!isFull()) {
11             rear = (rear + 1) % a.length;
12             a[rear] = val;
13             len++;
14             return true;
15         } else {
16             return false;
17         }
18     }
19 
20     public boolean deQueue() {
21         if (!isEmpty()) {
22             front = (front + 1) % a.length;
23             len--;
24             return true;
25         } else
26             return false;
27     }
28 
29     public int Front() {
30         return isEmpty() ? -1 : a[front];
31     }
32 
33     public int Rear() {
34         return isEmpty() ? -1 : a[rear];
35     }
36 
37     public boolean isEmpty() {
38         return len == 0;
39     }
40 
41     public boolean isFull() {
42         return len == a.length;
43     }
44 }