Created
December 20, 2019 03:25
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Implementation of Queue using Linked List
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class Node(object): | |
""" | |
Fundamental building block of a linked list | |
A node consists of a value and the next node location pointer | |
""" | |
def __init__(self, value): | |
self.val = value | |
self.next = None | |
class MyQueue(object): | |
""" | |
Queue implementation using LinkedList | |
Queue works in FIFO manner | |
""" | |
def __init__(self): | |
self.head = None | |
self.tail = None | |
def enqueueItem(self, item): | |
""" | |
Add new item to queue - O(1) | |
Queuing always happens at tail | |
If Queuing happens at head, dequeuing will require in O(n) | |
""" | |
newNode = Node(item) | |
if self.tail: | |
self.tail.next = newNode | |
self.tail = self.tail.next | |
else: | |
self.tail = newNode | |
self.head = self.tail | |
def dequeueItem(self): | |
""" | |
Dequeue item from queue - O(1) | |
""" | |
try: | |
self.head = self.head.next | |
except AttributeError as error: | |
self.head = None | |
def peekQueue(self): | |
""" | |
Peek the top value of the queue - O(1) | |
""" | |
try: | |
return self.head.val | |
except AttributeError as error: | |
return None | |
def isEmpty(self): | |
return self.head == self.tail | |
# if __name__ == "__main__": | |
# myQueue = MyQueue() | |
# print("Peek QValue", myQueue.peekQueue()) | |
# myQueue.enqueueItem(9) | |
# print("Peek QValue", myQueue.peekQueue()) | |
# myQueue.enqueueItem(10) | |
# print("Peek QValue", myQueue.peekQueue()) | |
# myQueue.dequeueItem() | |
# print("Peek QValue", myQueue.peekQueue()) | |
# myQueue.dequeueItem() | |
# print("Peek QValue", myQueue.peekQueue()) | |
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