3/17/2023 0 Comments Enqueue and dequeue![]() isEmpty() conventionally returns a boolean value: True if size is 0, else False. To prevent performing operations on an empty queue, the programmer is required to internally maintain the size of the queue which will be updated during enqueue and deque operations accordingly. This is similar to the peek operation in stacks, it returns the value of the element at the front without removing it. Naturally, the element inserted first will be at the front of the queue so we will remove the front element and let the element behind it be the new front element. Since queue follows the FIFO principle we need to remove the element of the queue which was inserted at first. ![]() Dequeue Operationĭequeue means removing an element from the queue. Similarly, a new element in a queue is inserted at the back of the queue. In a normal queue at a ticket counter, where does a new person go and stand to become a part of the queue? The person goes and stands in the back. In the next blog we will see about Linked list and its implemented in python.Enqueue means inserting an element in the queue. ![]() It needs no parameters and returns an integer.ĭeque Implementation class Deque: def _init_(self): ems = def isEmpty(self): return ems = def addFront(self, item): (item) def addRear(self, item): (0,item) def removeFront(self): return () def removeRear(self): return (0) def size(self): return len(ems) size() returns the number of items in the deque.It needs no parameters and returns a boolean value. isEmpty() tests to see whether the deque is empty.It needs no parameters and returns the item. removeRear() removes the rear item from the deque.removeFront() removes the front item from the deque.addRear(item) adds a new item to the rear of the deque.addFront(item) adds a new item to the front of the deque.It needs no parameters and returns an empty deque. Deque() creates a new deque that is empty.Now we will implement our own Deque class! Methods and Attributes It is up to us to make consistent use of the addition and removal operations. It is important to note that even through the deque can assume many of the characteristics of stacks and queues, It does not require the LIFO and FIFO ordering that are enforced by those data structure. In a sense, this hybrid linear structure provides all the capabilities of stacks and queues in a single data structure. Likewise, existing items can be removed from either end. New item can be added at either the front or the rare. What makes a deque different is the unrestrictive nature of adding and removing items. It has two ends, a front and a rear, and the items remain positioned in the collection. Queue Implementation class Queue: def _init_(self): ems = def isEmpty(self): return ems = def enqueue(self, item): (0,item) def dequeue(self): return () def size(self): return len(ems) q = Queue() q.size() 0 q.isEmpty() True q.enqueue(1) q.dequeue() 1 Deque OverviewĪ deque, also know as a double-ended queue, it is an ordered collection of items similar to the queue. It needs no parameters and returns an integer. size() returns the number of items in the queue.isEmpty() tests to see whether the queue is empty.dequeue() removes the front item from the queue.enqueue(item) adds a new item to the rear of the queue.It needs no parameters and returns an empty queue. Queue() creates a new queue that is empty.We will now build on our understanding of Queues by implementing our own class of Queue! Queue Methods and Attributesīefore we begin implementing our own queue, let’s review the attribute and methods it will have: Dequeue term describes removing the item from the front. The enqueue term describes when we add a new item to the rare of the queue.
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