# Design Circular Queue Problem

## Description

LeetCode Problem 622.

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.

Implementation the MyCircularQueue class:

• MyCircularQueue(k) Initializes the object with the size of the queue to be k.
• int Front() Gets the front item from the queue. If the queue is empty, return -1.
• int Rear() Gets the last item from the queue. If the queue is empty, return -1.
• boolean enQueue(int value) Inserts an element into the circular queue. Return true if the operation is successful.
• boolean deQueue() Deletes an element from the circular queue. Return true if the operation is successful.
• boolean isEmpty() Checks whether the circular queue is empty or not.
• boolean isFull() Checks whether the circular queue is full or not.

You must solve the problem without using the built-in queue data structure in your programming language.

Example 1:

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Input
["MyCircularQueue", "enQueue", "enQueue", "enQueue", "enQueue", "Rear", "isFull", "deQueue", "enQueue", "Rear"]
[[3], [1], [2], [3], [4], [], [], [], [4], []]
Output
[null, true, true, true, false, 3, true, true, true, 4]
Explanation
MyCircularQueue myCircularQueue = new MyCircularQueue(3);
myCircularQueue.enQueue(1); // return True
myCircularQueue.enQueue(2); // return True
myCircularQueue.enQueue(3); // return True
myCircularQueue.enQueue(4); // return False
myCircularQueue.Rear();     // return 3
myCircularQueue.isFull();   // return True
myCircularQueue.deQueue();  // return True
myCircularQueue.enQueue(4); // return True
myCircularQueue.Rear();     // return 4
``````

Constraints:

• 1 <= k <= 1000
• 0 <= value <= 1000
• At most 3000 calls will be made toenQueue, deQueue,Front,Rear,isEmpty, andisFull.

## Sample C++ Code

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class MyCircularQueue {
private:
vector<int> v;
int start = 0, len = 0;
public:
MyCircularQueue(int k): v(k) {}

bool enQueue(int value) {
if (isFull()) return false;
v[(start + len++) % v.size()] = value;
return true;
}

bool deQueue() {
if (isEmpty()) return false;
start = (start + 1) % v.size();
--len;
return true;
}

int Front() {
if (isEmpty()) return -1;
return v[start];
}

int Rear() {
if (isEmpty()) return -1;
return v[(start + len - 1) % v.size()];
}

bool isEmpty() {
return !len;
}

bool isFull() {
return len == v.size();
}
};

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