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[9/25] 622. Design Circular Queue

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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 enQueuedeQueueFrontRearisEmpty, and isFull.
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class MyCircularQueue:

    def __init__(self, k: int):
        self.max_size = k
        self.data = [0]*k
        self.front = 0
        self.back = -1
        
    def enQueue(self, value: int) -> bool:
        if self.isFull(): return False
        self.back = (self.back+1)%self.max_size
        self.data[self.back] = value
        return True
    
    def deQueue(self) -> bool:
        if self.isEmpty(): return False
        
        if self.front == self.back:
            self.front = 0
            self.back = -1
        else:
            self.front = (self.front+1)%self.max_size

        return True
    
    def Front(self) -> int:
        if self.isEmpty(): return -1
        return self.data[self.front]
    
    def Rear(self) -> int:
        if self.isEmpty(): return -1
        return self.data[self.back]
    
    def isEmpty(self) -> bool:
        return self.back == -1

    
    def isFull(self) -> bool:
        return self.back != -1 and (self.back+1)%self.max_size == self.front


# Your MyCircularQueue object will be instantiated and called as such:
# obj = MyCircularQueue(k)
# param_1 = obj.enQueue(value)
# param_2 = obj.deQueue()
# param_3 = obj.Front()
# param_4 = obj.Rear()
# param_5 = obj.isEmpty()
# param_6 = obj.isFull()
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