## 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.

Thoughts: Having two pointers , fast and slow and a size, capacity variables to track the current capacity status

1. Init: slow = 0; fast = -1; size = 0
``````class MyCircularQueue {
int size, slow, fast, C;
int data [];
/** Initialize your data structure here. Set the size of the queue to be k. */
public MyCircularQueue(int k) {
slow = 0; fast = -1; size = 0; C = k;
data = new int [k];
}

/** Insert an element into the circular queue. Return true if the operation is successful. */
public boolean enQueue(int value) {
if (isFull()) return false;
fast = (fast + 1) % C;
data[fast] = value;
size ++;
return true;
}

/** Delete an element from the circular queue. Return true if the operation is successful. */
public boolean deQueue() {
if(size == 0) return false;
slow = (slow + 1) % C;
size--;
return true;
}

/** Get the front item from the queue. */
public int Front() {
if (isEmpty()) return -1;
return data[slow];
}

/** Get the last item from the queue. */
public int Rear() {
if (isEmpty()) return -1;
return data[fast];
}

/** Checks whether the circular queue is empty or not. */
public boolean isEmpty() {
return size == 0;
}

/** Checks whether the circular queue is full or not. */
public boolean isFull() {
return size == C;
}
}

/**
* Your MyCircularQueue object will be instantiated and called as such:
* MyCircularQueue obj = new MyCircularQueue(k);
* boolean param_1 = obj.enQueue(value);
* boolean param_2 = obj.deQueue();
* int param_3 = obj.Front();
* int param_4 = obj.Rear();
* boolean param_5 = obj.isEmpty();
* boolean param_6 = obj.isFull();
*/
``````