Leetcode - Design Circular Queue (Python)

April 2021 Leetcode Challenge
Leetcode - Design Circular Queue #622
Difficulty: Medium

[bolvarsdad]

I've watched a ton of these videos trying to understand circular queues and this by far was the most easy to follow, and has the simplest and cleanest code. Thanks for your work.

[rutvijsupekar]

The most concise and clear explanations in all of youtube, thank you so much for your videos!

[janmichaelaustria]

Thanks for explaining the Rear method! I was wondering why it was -1

[julianelmasry]

What happens when tail ends up at the 0 index and you try to return list[-1] ?

[Cloud-]

why not use a linked list to implement the circular queue?

[jiakai]

Hi theres something i dont understand. The tail goes out of range after a few enQueues and deQueues because there are no more 'None'. Why do u not get this problem?

[edwardteach]

My Python Implementation:

class MyCircularQueue(object):

def __init__(self, k):
"""
:type k: int
"""
self.size = 0
self.k = k
self.arr = [None] * k
self.tail = -1 # -1 because we haven't added anything in the queue
self.head = 0

def enQueue(self, value):
"""
:type value: int
:rtype: bool
"""
if self.size >= self.k:
return False

self.tail = (self.tail + 1) % self.k
if not self.arr[self.tail]:
self.arr[self.tail] = value
self.size += 1
return True

def deQueue(self):
"""
:rtype: bool
"""
if self.isEmpty():
return False
self.arr[self.head] = None
self.head = (self.head + 1) % self.k
self.size -= 1
return True

def Front(self):
"""
:rtype: int
"""
if self.isEmpty():
return -1
return self.arr[self.head]

def Rear(self):
"""
:rtype: int
"""
if self.isEmpty():
return -1
return self.arr[self.tail]

def isEmpty(self):
"""
:rtype: bool
"""
return self.size == 0


def isFull(self):
"""
:rtype: bool
"""
return self.size == self.k