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# Design Circular Queue LeetCode Solution

## Problem – 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.

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:

``````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 to `enQueue``deQueue``Front``Rear``isEmpty`, and `isFull`.

### Design Circular Queue LeetCode Solution in Python

``````class MyCircularQueue:
def __init__(self, k: int):
self.data = [0] * k
self.maxSize = k
self.tail = -1
def enQueue(self, val: int) -> bool:
if self.isFull(): return False
self.tail = (self.tail + 1) % self.maxSize
self.data[self.tail] = val
return True
def deQueue(self) -> bool:
if self.isEmpty(): return False
return True
def Front(self) -> int:
return -1 if self.isEmpty() else self.data[self.head]
def Rear(self) -> int:
return -1 if self.isEmpty() else self.data[self.tail]
def isEmpty(self) -> bool:
return self.tail == -1
def isFull(self) -> bool:
return not self.isEmpty() and (self.tail + 1) % self.maxSize == self.head
``````

### Design Circular Queue LeetCode Solution in Java

``````class MyCircularQueue {
int maxSize, head = 0, tail = -1;
int[] data;
public MyCircularQueue(int k) {
data = new int[k];
maxSize = k;
}
public boolean enQueue(int val) {
if (isFull()) return false;
tail = (tail + 1) % maxSize;
data[tail] = val;
return true;
}
public boolean deQueue() {
if (isEmpty()) return false;
tail = -1;
return true;
}
public int Front() {
return isEmpty() ? -1 : data[head];
}
public int Rear() {
return isEmpty() ? -1 : data[tail];
}
public boolean isEmpty() {
return tail == -1;
}
public boolean isFull() {
return !isEmpty() && (tail + 1) % maxSize == head;
}
``````

### Design Circular Queue LeetCode Solution in C++

``````class MyCircularQueue {
public:
MyCircularQueue(int k) {
data.resize(k);
maxSize = k;
}
bool enQueue(int val) {
if (isFull()) return false;
tail = (tail + 1) % maxSize;
data[tail] = val;
return true;
}
bool deQueue() {
if (isEmpty()) return false;
return true;
}
int Front() {
return isEmpty() ? -1 : data[head];
}
int Rear() {
return isEmpty() ? -1 : data[tail];
}
bool isEmpty() {
return tail == -1;
}
bool isFull() {
return !isEmpty() && (tail + 1) % maxSize == head;
}
private:
int maxSize, head = 0, tail = -1;
vector<int> data;
};
``````
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