CREATING STACK IN PYTHON

CREATING STACK USING PYTHON

OPERATIONS:

1- PUSH

2- POP

OTHER OPERATIONS:

1- IS EMPTY

2- SIZE

3- TOP

CODE : 

We can implement stack using :

1- list

2- collections.deque

3- queue.LifoQueue

1 - IMPLEMENTING STACK USING LIST

CODE:

stack = []  // list is created to be used as stack
stack.append('a') // append() push the element in stack which is actually a list
stack.append('b')
stack.append('c')

print(stack.pop()) // pop() is used to pop / delete element on top of list

print(stack.pop())

print(stack.pop())

print(stack)

2- IMPLEMENTING STACK USING collections.deque

from collections import deque  // importing the library

stack = deque() // initializing a variable

stack.append('a') // append function to insert element

stack.append('b')

stack.append('c')

print(stack.pop())  // pop() function to remove the top element

print(stack.pop())

print(stack.pop())

print(stack)

3- IMPLEMENTING STACK USING queue module

Functions available in this module are :

1- get() - remove and return the element from queue

2- put(element) - put element in the queue

3- maxsize() - maximum elements allowed

4- empty() - check whether stack is empty or not

5- full() - check whether stack is full or not if maxsize is declared

6- qsize() - get number of items in queue

CODE:

from queue import LifoQueue
stack = LifoQueue(maxsize = 5) // initializing stack with maxsize = 5
print(stack.qsize()) // show the number of elements in the stack
stack.put('a')  // put() is used to push elements in the stack
stack.put('b')
stack.put('c')
print("Full: ", stack.full())  // is the stack full or does stack contain maxsize elements
print(stack.get()) // return and remove the top element of the stack
print(stack.get())
print(stack.get())
print("Is Empty : ", stack.empty()) // test is the stack empty or not

CREATING STACK USING STL

 STACK IN STL

Standard library provides us stack container with number of built in features.

STACK TEMPLATE :

template <class T, class Container = deque<T> > class stack;

MEMBER FUNCTIONS :

All these operations can be performed in 0(1)

empty  :  test whether the container is empty

size    : return the size of the container

top   : return the top element

push  : insert element

emplace  : construct and insert element

pop  : remove top element

swap  : swap contents

CODE ;

#include <iostream>
#include <stack>    // for using stack container
using namespace std;

int main()
{
int sum = 0;
stack<int> mystack; // declaring stack
mystack.push(21);   // inserting element
mystack.push(32);
mystack.push(23);
mystack.push(63);
mystack.push(212);

while (!mystack.empty()) {   // checking the empty condition
sum = sum + mystack.top();   // checking the top element
mystack.pop();               // performing pop operation
} 
cout << sum;
return 0;
}

 

IMPLEMENTING STACK USING LINKEDLIST

 IMPLEMENTING STACK USING LINKEDLIST

This provide us ability to define our own data structure and point it to another same data structure using pointers which can be done dynamically .

Here , Since we are using Linked list we will use malloc and free ( in C ) to allocate memory and then deallocate it when needed.

Structure or Linked list Node

Header Files

OPERATIONS

NOTE : Since  , performing operations on head is easy and efficient so  we will choose head node as top node and will perform all operations on head node 

1- PUSH

2- IS EMPTY

    

3- TOP

4- POP

IMPLEMENT STACK USING ARRAY

IMPLEMENTATION  USING ARRAY

DATA STRUCTURE

We will use structure to create stack that will have three things

1- Max Size : contains the maximum size stack can have or its capacity

2- Top : contains the index of the top element

3- items array or pointer to array : contains the elements of stack

Header Files :

operations to perform :

1- Initialization of stack

2- Getting size of stack

3- Check the status i.e. is the stack empty or not

4- Check the status i.e. is the stack full or not

5- Adding element to stack using Push operation

6- Removing the top of the stack using Pop operation

7- Getting the top of the stack

STACK : INTRODUCTION | OPERATIONS | REAL LIFE EXAMPLE | IMPLEMENTATION

 What Is Stack

. Linear Data Structure

TWO OPERATION : 

1 - PUSH : Entering the data on the top or at the end

2- POP : Remove the top element or latest element

So, Stack performs LIFO operation where LIFO stands for Last In First Out.

Nowadays every language has some more operations i.e. Peek, Is empty, Is full , size 

3 - PEEK : It help us to check the top entry without deleting it

4- IS EMPTY : this checks whether the stack is empty or not and provides boolean value (true / false)

5- IS FULL : this checks whether the stack is full or not in non dynamic data structure. If you are using standard library then it resize dynamically .

6- SIZE : this gives the size of the stack

Whenever you get stack , think it to be a data structure where you have to preform insertions and deletion on the same end what ever data structure you are using.

Real Life Example :

1- Plates stacked over one another

2- Stacked books

So , the book on top is the first book to be taken . Although it was the last book to place . Similarly

in marriages the top most dinner plate is the first plate to be taken and used.

APPLICATION OF STACK

1- Undo - Redo features 

2- Infix to Prefix or Postfix

3- Balancing the symbols

4- Used in Algorithms 

    a) Rat in maze

    b) N Queen Problem

    c) Tower of Hanoi

    d) Stock span problem

    e) Topological Sorting

    f) Strongly Connected Components

5- Syntax Parsing

6- Browser back button

7- Useful for performing operations like Backtracking in Programming

IMPLEMENTATION

You can use any data structure to perform this operation :

1- Array

2- Linkedlist

If you use standard library , you can use the data structure provided such as stack (we will see the implementation soon ) which is dynamic and provided certain operations.

Roadmap for full stack development

You can choose one of the following stack to start with full stack development :

LAMP stack: JavaScript - Linux - Apache - MySQL - PHP 

LEMP stack: JavaScript - Linux - Nginx - MySQL - PHP 

MEAN stack: JavaScript - MongoDB - Express - AngularJS - Node.js 

Django stack: JavaScript - Python - Django - MySQL 

Ruby on Rails: JavaScript - Ruby - SQLite - Rails

A full stack web developer is a person who can develop both client and server software.

Along HTML and CSS, one should also know :

• . Program a browser - like using JavaScript, jQuery, Angular, or Vue
• . Program a server  - like using PHP, ASP, Python, or Node
• . Program a database  - like using SQL, SQLite, or MongoDB

Some Top Skills : 

 

1. Front End Development

The artist in a Full Stack Web Developer is fully unleashed for Front End Development as it deals with the application parts that the users can see and interact with. The main technologies required for Front End development are HTML5, CSS3, and Javascript And that’s not all! Extra knowledge of third-party libraries like jQuery, Angular and ReactJs, etc. is also extremely helpful.

2. Back End Development

While front-end is the part of the application the user sees, the back end is often the mystical part that remains unseen. It handles the database operations, user authentication and application logic (Yeah, all the complicated things!). There are multiple languages that are used in Back End Development such as Java, Python, PHP, Ruby,Nodejs  etc. While every developer claims that their favorite language is the best, all of these languages have a market demand for suitable projects.

3. Databases

What can an application manage without data? Well, nothing at all!

And that’s why a database is the most important part of any application as it is required to store and access the data. So a Full Stack Web Developer needs to know the divide between Relational and NoSQL databases to understand the situations in which each would be useful. They should also be familiar with databases of each type such as MYSQL, MongoDB, etc. In addition to all this, knowledge of caching options such as Redis, Memcached, and Varnish would only be a plus!


4. Version Control System

There are multiple versions of an application. Now, what if a particular version needs to be recalled? That’s where the Version Control System comes in. It’s basically a system that records the changes made to the application files over time so that specific versions can be recalled later if required.

Git, in particular, is a Version Control System System that can be used to obtain the latest code, update parts of the code, and change other people’s code as well without creating a major mess of things!!!