PhilipDW183

Class Vertex:
  
    def __init__(self, key):
        self.id = key
        self.connectedTo = {}
        
    def addNeighbor(self, nbr, weight = 0):
        self.connectedTo[nbr] = weight
        
    def __str__(self):

PhilipDW183

class Queue:

    #create the constructor
    def __init__(self):
    
        #create an empty list as the items attribute
        self.items = []
        
    
    def enqueue(self, item):

PhilipDW183

#import the stack class we created
import stack

#instantiate the string
string  = "kcats a htiw gnirts a esrever ot woH"
#create an empty string 
reverse_string = ""
#create a new Stack
s = stack.Stack()

PhilipDW183

class Stack:
  
    #define the constructor
    def __init__(self):
        #We will initiate the stack with an empty list
        self.items = []
        
    def is_empty(self):
        """
        Returns whether the stack is empty or not

PhilipDW183

    def __str__(self):
        """Return a string representation of the Stack"""
        return str(self.items)

PhilipDW183

    def size(self):
        """Return the size of the Stack
        Runs in constant time O(1) as only checks the size"""
        #will return 0 if empty
        #so no need to check
        return len(self.items)

PhilipDW183

    def peek(self):
        """Return the final value from the Stack
        if there is a final value
        Runs in constant time O(1) as only finding the
        end of the list using the index
        """
        #if there are items in the Stack
        if self.items:
            #then return the item
            return self.items[-1]

PhilipDW183

    def pop(self)
        """Removes the last item from the Stack and returns it
        
        Runs in constant time O(1) as only an item is removed,
        no indices are changed
        """

        #as long as there are items in the list
        #then return the list item
        if self.items:

PhilipDW183

    def push(self, item):
        """
        Adds item to the end of the Stack, returns Nothing
        
        
        Runs in constant time O(1) as no indices are change
        as we add to the right of the list
        """
        
        #use standard list method append

PhilipDW183

    def is_empty(self):
        """
        Returns whether the stack is empty or not
        Runs in constant time O(1) as does not depend on size
        """
        #return True if empty
        #Return False if not
        return not self.items