stack-linked.py

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

class EmptyStackError(Exception):
    pass

class Node:

    def __init__(self,value):
        self.info = value 
        self.link = None
      
class Stack:

    def __init__(self):
        self.top = None
       
    def is_empty(self):
        return self.top == None
   
    def size(self):

        if self.is_empty():
            retun 0

        count=0
        p = self.top 
        while p is not None:
            count+=1
            p = p.link 
        return count

    def push(self, data):
        temp = Node(data)
        temp.link = self.top
        self.top = temp
       
    def peek(self):
        if self.is_empty():
            raise EmptyStackError("Stack is empty")
        return self.top.info
    
    def pop(self):      
        if self.is_empty():
            raise EmptyStackError("Stack is empty")
        popped = self.top.info
        self.top = self.top.link
        return popped

   def display(self):
        if self.is_empty():
            print("Stack is empty")
            return
        
        print("Stack is :   ")
        p = self.top 
        while p is not None:
            print(p.info , " ")
            p = p.link 
           
#####################################################################################
            
if __name__ == "__main__":
    st = Stack()

    while True:
        print("1.Push") 
        print("2.Pop") 
        print("3.Peek") 
        print("5.Size") 
        print("4.Display")  
        print("6.Quit") 
         
        choice = int(input("Enter your choice : "))

        if choice == 1:
            x=int(input("Enter the element to be pushed : "))
            st.push(x) 
        elif choice == 2:
            x=st.pop() 
            print("Popped element is : " , x) 
        elif choice == 3:
            print("Element at the top is : " , st.peek()) 
        elif choice == 4:
            print("Size of stack " , st.size())
        elif choice == 5:
            st.display()  
        elif choice == 6:
          break;
        else:
          print("Wrong choice") 
        print()