Data Structure

two ways: linear and non linear

Linear : list, stack, queue, array , link list

Non Linear : tree , graph

Stack : is a linear list  where insertion and deletion occurs from same end called TOP of the stack . Stack is also called LIFO. Stack has no variant. Stack can be implemented in Python using list.

Use of stack:

Reverse a word/line

Evaluate the math 
nested function calling/ Backtracking

Queue: is a linear list where insertion occurs from rear end and deletion from front end. Queue is also called FIFO. There are three types of Queue  ordinary queue, double ended queue and circular Queue. List can be implemented in Python using list

Use of Queue: 

Common operations performed on Data structure

insertion/deletion/Display(traversal)/Searching /sorting

Queue Operations in Python

def push(list,item):
    list.append(item)

def pushitem(list):
    item=int(input("Enter value"))
    list.append(item)

def popitem(list):
    if(list==[]):
        print("Queue is empty")
    else:
        print("Deleted item",list[0])
        del(list[0])

def display(list):
    if(list==[]):
        print("Queue is empty")
    else:
        
        for i in  list:
            print(i)


Stack Operations in Python

list=[ ]

def push(list):

    item=int(input("Enter value"))

    list.append(item)

def popitem(list):

    if(list==[]):

        print("Stack is empty")

    else:

       print("Deleted item",list.pop())

def display(list):

  if(list==[]):

      print("stack is empty")

  else:

     print(list[::-1])

                        

n=int(input("Enter Your choice 1.push 2.pop 3.display 4.exit "))               

while(n!=4):

  if(n==1):

    push(list)

  elif (n==2):

    popitem(list)

  elif(n==3):

    display(list)

  else:

    break

  n=int(input("Enter Your choice 1.push 2.pop 3.display 4.exit "))