deque-circular.py

# Copyright (C) Deepali Srivastava - All Rights Reserved
# This code is part of DSA course available on CourseGalaxy.com  

class EmptyQueueError(Exception):
    pass
       
class Deque:

    def __init__(self,default_size=10):
        self.items = [None] * default_size
        self.front = 0
        self.count = 0
    
    def is_empty(self):
        return self.count == 0
    
    def size(self):
        return self.count
    
    def insert_front(self, item):
        if self.count == len(self.items):
            self.resize( 2*len(self.items) )

        self.front = (self.front - 1) % len(self.items)
        self.items[self.front] = item
        self.count+=1
        
    def insert_rear(self, item):
        if self.count == len(self.items):
            self.resize( 2*len(self.items) )
            
        i = (self.front + self.count) % len(self.items)
        self.items[i] = item
        self.count+=1
        
    def delete_front(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is empty")

        x = self.items[self.front]
        self.items[self.front] = None
        self.front = (self.front + 1) % len(self.items)
        self.count-=1
        return x
       
    def delete_rear(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is empty")
        rear = (self.front + self.count - 1) % len(self.items)
        x = self.items[rear]
        self.items[rear] = None
        self.count-=1
        return x
        
    def first(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is empty")
        return self.items[self.front]

    def last(self):
        if self.is_empty():
            raise EmptyQueueError("Queue is empty")
        rear = (self.front + self.count - 1) % len(self.items)
        return self.items[rear]    

    def display(self):
        print(self.items)

    def resize(self,newsize):
        old_list = self.items
        self.items = [None]*newsize
        i = self.front
        for j in range(self.count):
            self.items[j] = old_list[i]
            i = (1+i)%len(old_list)
        self.front = 0 
        
####################################################################

if __name__ == "__main__":
    qu = Deque(6)

    while True:
        print("1.Insert at the front end")
        print("2.Insert at the rear end")
        print("3.Delete from front end")
        print("4.Delete from rear end")
        print("5.Display first element")
        print("6.Display last element")
        print("7.Display")
        print("8.Size")
        print("9.Quit")
             
        choice = int(input("Enter your choice : "))

        if choice == 1:
            x=int(input("Enter the element : "))
            qu.insert_front(x)
        elif choice== 2:
            x=int(input("Enter the element : "))
            qu.insert_rear(x)
        elif choice == 3:
            x = qu.delete_front()
            print("Element deleted from front end is  ", x)
        elif choice == 4:
            x = qu.delete_rear()
            print("Element deleted from rear end is  ", x)
        elif choice == 5:
            print("First element is  ", qu.first())
        elif choice == 6:
            print("Last element is  ", qu.last())
        elif choice == 7:
            qu.display()
        elif choice == 8:
            print("Size of queue " , qu.size())
        elif choice == 9:
            break
        else:
            print("Wrong choice")
        print()