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Commit 52cc8f4

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Added Queue and QueueLL code.
1 parent 2dd289b commit 52cc8f4

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3 files changed

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3 files changed

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‎Queues/queues.py‎

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import os
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class Queue:
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def __init__(self):
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self._data = []
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def __len__(self):
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'''
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Returns length of Queue
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'''
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return len(self._data)
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def isempty(self):
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'''
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Returns True if Queue is empty, otherwise False.
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'''
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return self.__len__ == 0
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def enqueue(self, e):
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'''
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Adds the passed element at the end of the list.
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That means, it enqueues element.
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'''
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self._data.append(e)
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def dequeue(self):
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'''
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Removes element from the beginning of the list and
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returns the removed element.
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That means, it dequeues.
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'''
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if self.isempty():
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print("Queue is empty.")
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return
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return self._data.pop(0)
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def first(self):
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'''
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Peeks and return the first element in the Queue.
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'''
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if self.isempty():
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print("Queue is empty.")
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return
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return self._data[0]
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def display(self):
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'''
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Utility function to display the Queue.
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'''
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if self.isempty():
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print("Queue is empty.")
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else:
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print("Front", end=' <--')
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for i in self._data:
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print(i, end='<--')
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print(" Rear")
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###############################################################################
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def options():
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'''
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Prints Menu for operations
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'''
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options_list = ['Enqueue', 'Dequeue', 'First',
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'Display Queue', 'Exit']
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print("MENU")
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for i, option in enumerate(options_list):
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print(f'{i + 1}. {option}')
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choice = int(input("Enter choice: "))
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return choice
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def switch_case(choice):
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'''
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Switch Case for operations
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'''
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os.system('cls')
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if choice == 1:
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elem = int(input("Enter item to Enqueue: "))
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Q.enqueue(elem)
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elif choice == 2:
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print('Dequeued item is: ', Q.dequeue())
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elif choice == 3:
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print("First item is: ", Q.first())
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elif choice == 4:
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print("Queue: ")
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Q.display()
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print("\n")
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elif choice == 5:
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import sys
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sys.exit()
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###############################################################################
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Q = Queue()
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while True:
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choice = options()
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switch_case(choice)

‎Queues/queuesLL.py‎

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import os
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class _Node:
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'''
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Creates a Node with two fields:
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1. element (accesed using ._element)
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2. link (accesed using ._link)
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'''
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__slots__ = '_element', '_link'
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def __init__(self, element, link):
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'''
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Initialses _element and _link with element and link respectively.
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'''
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self._element = element
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self._link = link
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class QueueLL:
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'''
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Consists of member funtions to perform different
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operations on the linked list.
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'''
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def __init__(self):
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'''
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Initialses head, tail and size with None, None and 0 respectively.
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'''
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self._head = None
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self._tail = None
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self._size = 0
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def __len__(self):
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'''
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Returns length of Queue
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'''
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return self._size
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def isempty(self):
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'''
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Returns True if Queue is empty, otherwise False.
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'''
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return self._size == 0
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def enqueue(self, e):
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'''
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Adds the passed element at the end of the linked list.
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That means, it enqueues element.
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'''
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newest = _Node(e, None)
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if self.isempty():
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self._head = newest
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else:
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self._tail._link = newest
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self._tail = newest
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self._size += 1
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def dequeue(self):
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'''
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Removes element from the beginning of the linked list and
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returns the removed element.
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That means, it dequeues.
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'''
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if self.isempty():
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print("Queue is Empty. Cannot perform dequeue operation.")
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return
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e = self._head._element
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self._head = self._head._link
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self._size = self._size - 1
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if self.isempty():
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self._tail = None
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return e
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def first(self):
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'''
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Peeks and return the first element in the Queue.
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'''
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if self.isempty():
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print("Queue is Empty.")
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return
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e = self._head._element
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return e
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def display(self):
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'''
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Utility function to display the Queue.
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'''
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if self.isempty() == 0:
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p = self._head
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print("Front", end=' <--')
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while p:
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print(p._element, end='<--')
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p = p._link
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print(" Rear")
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else:
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print("Empty")
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###############################################################################
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def options():
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'''
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Prints Menu for operations
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'''
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options_list = ['Enqueue', 'Dequeue', 'First',
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'Display Queue', 'Exit']
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print("MENU")
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for i, option in enumerate(options_list):
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print(f'{i + 1}. {option}')
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choice = int(input("Enter choice: "))
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return choice
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def switch_case(choice):
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'''
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Switch Case for operations
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'''
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os.system('cls')
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if choice == 1:
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elem = int(input("Enter item to Enqueue: "))
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Q.enqueue(elem)
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elif choice == 2:
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print('Dequeued item is: ', Q.dequeue())
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elif choice == 3:
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print("First item is: ", Q.first())
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elif choice == 4:
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print("Queue: ")
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Q.display()
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print("\n")
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elif choice == 5:
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import sys
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sys.exit()
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###############################################################################
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Q = QueueLL()
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while True:
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choice = options()
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switch_case(choice)

‎README.md‎

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1. [Stack using inbuilt Python List](Stacks/stack.py)
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2. [Stack using Linked List](Stacks/stackLL.py)
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### 3. Queue
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1. [Queue using inbuilt Python List](Queues/queues.py)
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2. [Queue using Linked List](Queues/queuesLL.py)

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