Implement Stack using Linked List Python

PROGRAM TO IMPLEMENT STACK USING SINGLY LINKED LIST

class Node:

     

    # Class to create nodes of linked list

    # constructor initializes node automatically

    def __init__(self,data):

        self.data = data

        self.next = None

     

class Stack:

     

    # head is default NULL

    def __init__(self):

        self.head = None

     

    # Checks if stack is empty

    def isempty(self):

        if self.head == None:

            return True

        else:

            return False

     

    # Method to add data to the stack

    # adds to the start of the stack

    def push(self,data):

         

        if self.head == None:

            self.head=Node(data)

             

        else:

            newnode = Node(data)

            newnode.next = self.head

            self.head = newnode

     

    # Remove element that is the current head (start of the stack)

    def pop(self):

         

        if self.isempty():

            return None

             

        else:

            # Removes the head node and makes

            #the preceeding one the new head

            poppednode = self.head

            self.head = self.head.next

            poppednode.next = None

            return poppednode.data

     

    # Returns the head node data

    def peek(self):

         

        if self.isempty():

            return None

             

        else:

            return self.head.data

     

    # Prints out the stack    

    def display(self):

         

        iternode = self.head

        if self.isempty():

            print("Stack Underflow")

         

        else:

             

            while(iternode != None):

                 

                print(iternode.data,"->",end = " ")

                iternode = iternode.next

            return

         

# Driver code

MyStack = Stack()

 

MyStack.push(11)

MyStack.push(22)

MyStack.push(33)

MyStack.push(44)

 

# Display stack elements

MyStack.display()

 

# Print top element of stack

print("\nTop element is ",MyStack.peek())

 

# Delete top elements of stack

MyStack.pop()

MyStack.pop()

 

# Display stack elements

MyStack.display()

 

# Print top element of stack

print("\nTop element is ", MyStack.peek())




OUTPUT:

44->33->22->11->
Top element is 44
22->11->
Top element is 22

CREDITS: https://www.geeksforgeeks.org/implement-a-stack-using-singly-linked-list/