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Implement a queue using singly-linked list

John Main answered on February 12, 2024 Popularity 3/10 Helpfulness 1/10

answer Implement a queue using singly-linked list

Implement a queue using singly-linked list

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#an exception to be raised by an empty Queue
class Empty(Exception):
    pass

class Queue:
    class _Node:
        def __init__(self, e, n):
            self._element = e #Users element
            self._next = n #The next node in the list

    def __init__(self):
        self._head = None #Reference the first node
        self._tail = None #refernce the last node
        self._size = 0    #The number of elements in the queue

    def __len__(self):
        return self._size 

    def is_empty(self):
         return len(self) == 0

    def first(self):
        if self.is_empty():
            raise Empty("Queue is empty.")
        return self._head._element

    def enqueue(self, e):
        #add a new element at the back
        newnode = self._Node(e, None)
        if self.is_empty():
            self._head = newnode #if the queue is empty, the newnode becomes the head
        else:
            self._tail._next = newnode  #if the queue is not empty, the last node points to the new node
        self._tail = newnode #The new node becomes the tail
        self._size += 1

    def dequeue(self):
        if self.is_empty():
            raise Empty("Queue is empty.")
        element = self._head._element
        self._head = self._head._next # Make the next node the new head
        self._size -= 1
        return element

# test the stack
Q = Queue()
Q.enqueue(100)
Q.enqueue(200)
Q.enqueue(300)
Q.enqueue(400)
Q.enqueue(500)
print("Size: ", len(Q))
print(Q.first())
while not Q.is_empty():
    print(Q.dequeue())

print("Size:", len(Q))

Popularity 3/10 Helpfulness 1/10 Language python

Source: www.pynerds.com

Tags: python queue singly-linked-list using

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Contributed on Feb 12 2024

John Main

0 Answers Avg Quality 2/10

Implement a queue using singly-linked list

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