class Stack:
"""Basic stack (LIFO) implementation using a singly linked list"""
def __init__(self):
"""Stack constructor"""
self.__list = LinkedList()
def size(self):
"""Determines the size of the stack
Time complexity: O(1)
"""
return self.__list.size
def empty(self):
"""Determines if the stack is empty or not
Time complexity: O(1)
"""
return self.__list.empty()
def push(self, data):
"""Pushes an item onto the stack (head)
Time complexity: O(1)
"""
return self.__list.addHead(data)
def pop(self):
"""Removes an item off of the stack (head)
Time complexity: O(1)
"""
return self.__list.remove(0) if not self.empty() else None
def pretty_print(self):
"""Pretty prints the stack in the following format:
(head) -> ... -> (tail)
"""
self.__list.pretty_print()
class Queue:
"""Basic queue (FIFO) implementation using a singly linked list"""
def __init__(self):
"""Queue constructor"""
self.__list = LinkedList()
def peek(self):
"""Returns the node at front of the queue without removing it"""
return self.__list.get(0) if not self.is_empty() else None
def dequeue(self):
"""Removes an item of the front of the queue (head)
Time complexity: O(1)
"""
return self.__list.remove(0) if not self.is_empty() else None
def enqueue(self, data):
"""Pushes an item onto the back of the queue (tail)
Time complexity: O(1)
"""
return self.__list.add(data)
def size(self):
"""Determines the size of the queue
Time complexity: O(1)
"""
return self.__list.size
def is_empty(self):
"""Determines if the queue is empty or not
Time complexity: O(1)
"""
return self.__list.is_empty()
def clear(self):
"""Clears out (empties) the queue.
Time complexity: O(1)
"""
# Deallocate memory
del self.__list
# Create new linked list
self.__list = LinkedList()
def pretty_print(self):
"""Pretty prints the queue in the following format:
(head) -> ... -> (tail)
"""
self.__list.pretty_print()