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Deepali-SrivastavaDeepali-Srivastava
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Queue in Python
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‎stack-and-queue/circular-queue.py

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# Copyright (C) Deepali Srivastava - All Rights Reserved
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# This code is part of DSA course available on CourseGalaxy.com
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class EmptyQueueError(Exception):
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pass
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class Queue:
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def __init__(self,default_size=10):
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self.items = [None] * default_size
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self.front = 0
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self.count = 0
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def is_empty(self):
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return self.count == 0
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def size(self):
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return self.count
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def enqueue(self, item):
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if self.count == len(self.items):
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self.resize( 2*len(self.items) )
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i = (self.front + self.count) % len(self.items)
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self.items[i] = item
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self.count+=1
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def dequeue(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is empty")
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x = self.items[self.front]
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self.items[self.front] = None
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self.front = (self.front + 1) % len(self.items)
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self.count-=1
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return x
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def peek(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is empty")
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return self.items[self.front]
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def display(self):
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print(self.items)
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def resize(self,newsize):
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old_list = self.items
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self.items = [None]*newsize
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i = self.front
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for j in range(self.count):
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self.items[j] = old_list[i]
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i = (1+i)%len(old_list)
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self.front = 0
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###########################################################
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if __name__ == "__main__":
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qu = Queue(6)
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while True:
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print("1.Enqueue")
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print("2.Dequeue")
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print("3.Peek")
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print("4.Size")
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print("5.Display")
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print("6.Quit")
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choice = int(input("Enter your choice : "))
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if choice == 1:
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x=int(input("Enter the element : "))
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qu.enqueue(x)
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elif choice == 2:
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x=qu.dequeue()
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print("Element deleted from the queue is : " , x)
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elif choice == 3:
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print("Element at the front end is " , qu.peek())
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elif choice == 4:
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print("Size of queue ", qu.size())
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elif choice == 5:
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qu.display()
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elif choice == 6:
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break
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else:
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print("Wrong choice")
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print()

‎stack-and-queue/queue-array-1.py

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# Copyright (C) Deepali Srivastava - All Rights Reserved
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# This code is part of DSA course available on CourseGalaxy.com
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class EmptyQueueError(Exception):
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pass
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class Queue:
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def __init__(self):
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self.items = []
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self.front = 0
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def is_empty(self):
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return self.front == len(self.items)
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def size(self):
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return len(self.items)-self.front
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def enqueue(self, item):
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self.items.append(item)
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def dequeue(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is Empty")
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x = self.items[self.front]
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self.items[self.front] = None
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self.front = self.front + 1
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return x
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def peek(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is Empty")
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return self.items[self.front]
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def display(self):
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print(self.items)
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###########################################################
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if __name__ == "__main__":
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qu = Queue()
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while True:
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print("1.Enqueue")
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print("2.Dequeue")
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print("3.Peek")
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print("4.Size")
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print("5.Display")
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print("6.Quit")
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choice = int(input("Enter your choice : "))
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if choice == 1:
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x=int(input("Enter the element : "))
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qu.enqueue(x)
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elif choice == 2:
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x=qu.dequeue()
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print("Element deleted from the queue is : " , x)
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elif choice == 3:
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print("Element at the front end is " , qu.peek())
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elif choice == 4:
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print("Size of queue ", qu.size())
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elif choice == 5:
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qu.display()
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elif choice == 6:
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break;
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else:
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print("Wrong choice")
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print()
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‎stack-and-queue/queue-array.py

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# Copyright (C) Deepali Srivastava - All Rights Reserved
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# This code is part of DSA course available on CourseGalaxy.com
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class EmptyQueueError(Exception):
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pass
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class Queue:
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def __init__(self):
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self.items = []
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def is_empty(self):
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return self.items == []
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def size(self):
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return len(self.items)
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def enqueue(self, item):
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self.items.append(item)
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def dequeue(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is Empty")
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return self.items.pop(0)
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def peek(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is Empty")
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return self.items[0]
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def display(self):
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print(self.items)
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###########################################################
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if __name__ == "__main__":
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qu = Queue()
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while True:
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print("1.Enqueue")
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print("2.Dequeue")
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print("3.Peek")
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print("4.Size")
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print("5.Display")
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print("6.Quit")
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choice = int(input("Enter your choice : "))
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if choice == 1:
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x=int(input("Enter the element : "))
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qu.enqueue(x)
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elif choice == 2:
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x=qu.dequeue()
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print("Element deleted from the queue is : " , x)
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elif choice == 3:
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print("Element at the front end is " , qu.peek())
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elif choice == 4:
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print("Size of queue ", qu.size())
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elif choice == 5:
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qu.display()
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elif choice == 6:
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break;
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else:
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print("Wrong choice")
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print()
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‎stack-and-queue/queue-circular-linked.py

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# Copyright (C) Deepali Srivastava - All Rights Reserved
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# This code is part of DSA course available on CourseGalaxy.com
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class EmptyQueueError(Exception):
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pass
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class Node:
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def __init__(self,value):
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self.info = value
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self.link = None
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class Queue:
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def __init__(self):
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self.rear = None
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def is_empty(self):
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return self.rear == None
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def size(self):
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if self.is_empty():
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return 0
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n = 0
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p = self.rear.link
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while True:
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n+=1
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p = p.link
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if p == self.rear.link:
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break
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return n
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def enqueue(self, data):
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temp = Node(data)
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if self.is_empty():
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self.rear = temp
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self.rear.link = self.rear
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else:
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temp.link = self.rear.link
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self.rear.link = temp
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self.rear = temp
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def dequeue(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is Empty")
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if self.rear.link == self.rear: #List has only one node
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temp = self.rear
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self.rear = None
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else:
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temp = self.rear.link
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self.rear.link = self.rear.link.link
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return temp.info
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def peek(self):
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if self.is_empty():
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raise EmptyQueueError("Queue is Empty")
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return self.rear.link.info
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def display(self):
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if self.is_empty():
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print("List is empty")
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return
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p = self.rear.link
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while True:
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print(p.info , " ",end='')
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p = p.link
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if p == self.rear.link:
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break
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print()
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########################################################################
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if __name__ == "__main__":
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qu = Queue()
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while True:
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print("1.Enqueue")
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print("2.Dequeue")
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print("3.Peek")
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print("4.Size")
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print("5.Display")
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print("6.Quit")
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choice = int(input("Enter your choice : "))
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if choice == 1:
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x=int(input("Enter the element : "))
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qu.enqueue(x)
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elif choice == 2:
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x=qu.dequeue()
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print("Element deleted from the queue is : " , x)
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elif choice == 3:
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print("Element at the front end is " , qu.peek())
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elif choice == 4:
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print("Size of queue ", qu.size())
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elif choice == 5:
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qu.display()
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elif choice == 6:
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break;
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else:
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print("Wrong choice")
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print()
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