622 Design Circular Queue.py

#!/usr/bin/python3
"""
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.
"""


class MyCircularQueue:

    def __init__(self, k: int):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        """
        self.head = 0
        self.tail = -1
        self.sz = 0
        self.k = k
        self.lst = [None for _ in range(k)]


    def enQueue(self, value: int) -> bool:
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        """
        if self.sz >= self.k:
            return False

        self.tail += 1
        self.lst[self.tail % self.k] = value
        self.sz += 1
        return True

    def deQueue(self) -> bool:
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        """
        if self.sz <= 0:
            return False

        self.lst[self.head % self.k] = None
        self.head += 1
        self.sz -= 1
        return True

    def Front(self) -> int:
        """
        Get the front item from the queue.
        """
        ret = self.lst[self.head % self.k]
        return ret if ret is not None else -1

    def Rear(self) -> int:
        """
        Get the last item from the queue.
        """
        ret = self.lst[self.tail % self.k]
        return ret if ret is not None else -1

    def isEmpty(self) -> bool:
        """
        Checks whether the circular queue is empty or not.
        """
        return self.sz == 0

    def isFull(self) -> bool:
        """
        Checks whether the circular queue is full or not.
        """
        return self.sz == self.k


# 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()