design_circular_queue.py

"""

622. Design Circular Queue
Medium

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.

"""

# V0 
# IDEA : ARRAY
# https://leetcode.com/problems/design-circular-queue/solution/
class MyCircularQueue:

    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        """
        self.queue = [0]*k
        self.headIndex = 0
        self.count = 0
        self.capacity = k

    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        """
        if self.count == self.capacity:
            return False
        self.queue[(self.headIndex + self.count) % self.capacity] = value
        self.count += 1
        return True

    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        """
        if self.count == 0:
            return False
        self.headIndex = (self.headIndex + 1) % self.capacity
        self.count -= 1
        return True

    def Front(self):
        """
        Get the front item from the queue.
        """
        if self.count == 0:
            return -1
        return self.queue[self.headIndex]

    def Rear(self):
        """
        Get the last item from the queue.
        """
        # empty queue
        if self.count == 0:
            return -1
        return self.queue[(self.headIndex + self.count - 1) % self.capacity]

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

    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        """
        return self.count == self.capacity

# V0'
# IDEA : LINKED LIST
# https://leetcode.com/problems/design-circular-queue/solution/
class Node:
    def __init__(self, value, nextNode=None):
        self.value = value
        self.next = nextNode

class MyCircularQueue:

    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        """
        self.capacity = k
        self.head = None
        self.tail = None
        self.count = 0

    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        """
        if self.count == self.capacity:
            return False
        
        if self.count == 0:
            self.head = Node(value)
            self.tail = self.head
        else:
            newNode = Node(value)
            self.tail.next = newNode
            self.tail = newNode
        self.count += 1
        return True


    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        """
        if self.count == 0:
            return False
        self.head = self.head.next
        self.count -= 1
        return True


    def Front(self):
        """
        Get the front item from the queue.
        """
        if self.count == 0:
            return -1
        return self.head.value

    def Rear(self):
        """
        Get the last item from the queue.
        """
        # empty queue
        if self.count == 0:
            return -1
        return self.tail.value
    
    def isEmpty(self):
        """
        Checks whether the circular queue is empty or not.
        """
        return self.count == 0

    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        """
        return self.count == self.capacity

# V1
# IDEA : ARRAY
# https://leetcode.com/problems/design-circular-queue/solution/
class MyCircularQueue:

    def __init__(self, k: int):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        """
        self.queue = [0]*k
        self.headIndex = 0
        self.count = 0
        self.capacity = k

    def enQueue(self, value: int) -> bool:
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        """
        if self.count == self.capacity:
            return False
        self.queue[(self.headIndex + self.count) % self.capacity] = value
        self.count += 1
        return True

    def deQueue(self) -> bool:
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        """
        if self.count == 0:
            return False
        self.headIndex = (self.headIndex + 1) % self.capacity
        self.count -= 1
        return True

    def Front(self) -> int:
        """
        Get the front item from the queue.
        """
        if self.count == 0:
            return -1
        return self.queue[self.headIndex]

    def Rear(self) -> int:
        """
        Get the last item from the queue.
        """
        # empty queue
        if self.count == 0:
            return -1
        return self.queue[(self.headIndex + self.count - 1) % self.capacity]

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

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

# V1
# IDEA : ARRAY V2 + LOCK
# https://leetcode.com/problems/design-circular-queue/solution/
from threading import Lock

class MyCircularQueue:

    def __init__(self, k: int):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        """
        self.queue = [0]*k
        self.headIndex = 0
        self.count = 0
        self.capacity = k
        # the additional attribute to protect the access of our queue
        self.queueLock = Lock()

    def enQueue(self, value: int) -> bool:
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        """
        # automatically acquire the lock when entering the block
        with self.queueLock:
            if self.count == self.capacity:
                return False
            self.queue[(self.headIndex + self.count) % self.capacity] = value
            self.count += 1
        # automatically release the lock when leaving the block
        return True

# V1
# IDEA : LINKED LIST
# https://leetcode.com/problems/design-circular-queue/solution/
class Node:
    def __init__(self, value, nextNode=None):
        self.value = value
        self.next = nextNode

class MyCircularQueue:

    def __init__(self, k: int):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        """
        self.capacity = k
        self.head = None
        self.tail = None
        self.count = 0

    def enQueue(self, value: int) -> bool:
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        """
        if self.count == self.capacity:
            return False
        
        if self.count == 0:
            self.head = Node(value)
            self.tail = self.head
        else:
            newNode = Node(value)
            self.tail.next = newNode
            self.tail = newNode
        self.count += 1
        return True


    def deQueue(self) -> bool:
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        """
        if self.count == 0:
            return False
        self.head = self.head.next
        self.count -= 1
        return True


    def Front(self) -> int:
        """
        Get the front item from the queue.
        """
        if self.count == 0:
            return -1
        return self.head.value

    def Rear(self) -> int:
        """
        Get the last item from the queue.
        """
        # empty queue
        if self.count == 0:
            return -1
        return self.tail.value
    
    def isEmpty(self) -> bool:
        """
        Checks whether the circular queue is empty or not.
        """
        return self.count == 0

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

# V1
# https://blog.csdn.net/qq_32424059/article/details/86998300
class MyCircularQueue(object):
 
    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        :type k: int
        """
        self.queue = [""] * k
        self.max_length = k
        self.start = -1
        self.end = -1
 
    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        :type value: int
        :rtype: bool
        """
        
        if not self.isFull():
            if self.start == -1:
                self.start = 0
            self.end = (self.end + 1) % self.max_length
            self.queue[self.end] = value
            return True
        else:
            return False
        
        
 
    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        :rtype: bool
        """
        if not self.isEmpty():       
            if self.start == self.end: # the last element
                self.start, self.end = -1, -1
                # self.end = -1
            else:
                self.start = (self.start + 1) % self.max_length
            return True
        else:
            return False
        
 
    def Front(self):
        """
        Get the front item from the queue.
        :rtype: int
        """
        return -1 if self.isEmpty() else self.queue[self.start]
 
 
    def Rear(self):
        """
        Get the last item from the queue.
        :rtype: int
        """
        return -1 if self.isEmpty() else self.queue[self.end]
 
    def isEmpty(self):
        """
        Checks whether the circular queue is empty or not.
        :rtype: bool
        """
        return self.start == -1 and self.end == -1
 
    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        :rtype: bool
        """
        return (self.end + 1) % self.max_length == self.start

# V1'
# https://blog.csdn.net/fuxuemingzhu/article/details/81027583
class MyCircularQueue(object):

    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        :type k: int
        """
        self.queue = []
        self.size = k
        self.front = 0
        self.rear = 0

    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        :type value: int
        :rtype: bool
        """
        if self.rear - self.front < self.size:
            self.queue.append(value)
            self.rear += 1
            return True
        else:
            return False

    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        :rtype: bool
        """
        if self.rear - self.front > 0:
            self.front += 1
            return True
        else:
            return False

    def Front(self):
        """
        Get the front item from the queue.
        :rtype: int
        """
        if self.isEmpty():
            return -1
        else:
            return self.queue[self.front]

    def Rear(self):
        """
        Get the last item from the queue.
        :rtype: int
        """
        if self.isEmpty():
            return -1
        else:
            return self.queue[self.rear - 1]

    def isEmpty(self):
        """
        Checks whether the circular queue is empty or not.
        :rtype: bool
        """
        return self.front == self.rear

    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        :rtype: bool
        """
        return self.rear - self.front == self.size
# 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()

# V1''
# https://blog.csdn.net/fuxuemingzhu/article/details/81027583
class MyCircularQueue(object):

    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        :type k: int
        """
        self.queue = []
        self.size = k
        self.rear = 0

    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        :type value: int
        :rtype: bool
        """
        if not self.isFull():
            self.queue.append(value)
            self.rear += 1
            return True
        else:
            return False

    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        :rtype: bool
        """
        if not self.isEmpty():
            self.queue.pop(0)
            self.rear -= 1
            return True
        else:
            return False

    def Front(self):
        """
        Get the front item from the queue.
        :rtype: int
        """
        if self.isEmpty():
            return -1
        else:
            return self.queue[0]

    def Rear(self):
        """
        Get the last item from the queue.
        :rtype: int
        """
        if self.isEmpty():
            return -1
        else:
            return self.queue[self.rear - 1]

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

    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        :rtype: bool
        """
        return self.rear == self.size


# 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()

# V1'''
# https://blog.csdn.net/fuxuemingzhu/article/details/81027583
class MyCircularQueue(object):

    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        :type k: int
        """
        self.queue = []
        self.size = k

    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        :type value: int
        :rtype: bool
        """
        if not self.isFull():
            self.queue.append(value)
            return True
        else:
            return False

    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        :rtype: bool
        """
        if not self.isEmpty():
            self.queue.pop(0)
            return True
        else:
            return False

    def Front(self):
        """
        Get the front item from the queue.
        :rtype: int
        """
        if self.isEmpty():
            return -1
        else:
            return self.queue[0]

    def Rear(self):
        """
        Get the last item from the queue.
        :rtype: int
        """
        if self.isEmpty():
            return -1
        else:
            return self.queue[-1]

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

    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        :rtype: bool
        """
        return len(self.queue) == self.size

# V2