Senior Software Engineer

import java.util.ArrayList;
import java.util.PriorityQueue;

public class Solution {

public static ArrayList kLargest(int input[], int k) {
int i=0;
PriorityQueue pq=new PriorityQueue<>();
ArrayList arr=new ArrayList<>();
while(i pq.add(input[i]);
i++;
}
while(i if(pq.peek() pq.poll();
pq.add(input[i]);
}
i++;
}
while(!pq.isEmpty()){
arr.add(pq.poll());
}
return arr;

}
}

Tip 1 : You can solve using partitioning this problem as the approach told in coding ninja lectures.
Tip 2 : You can solve using a 2D matrix problem here you have to just print all boundary elements and diagonal elements.
 

Difference between Nodejs and JavaScript : 
S.No Javascript NodeJS
1. 
Javascript is a programming language that is used for writing scripts on the website. NodeJS is a Javascript runtime environment.
2. Javascript can only be run in the browsers. We can run Javascript outside the browser with the help of NodeJS.
3. It is basically used on the client-side. It is mostly used on the server-side.
4. Javascript is capable enough to add HTML and play with the DOM. Nodejs does not have capability to add HTML tags.
5. Javascript can run in any browser engine as like JS core in safari V8 is the Javascript engine inside of node.js that parses and runs Javascript. 
and Spidermonkey in Firefox. 
6. Javascript is used in frontend development. Nodejs is used in server-side development.
7. Some of the javascript frameworks are RamdaJS, TypedJS, etc. Some of the Nodejs modules are Lodash, express etc. These modules are to be imported from npm. 



difference node & express

Feature Express.js Node.js
Level of features More features than Node.js. Fewer features.
Building Block It is built on Node.js. It is built on Google's V8 engine.


Middleware-
functions that have access 1.request object ( req ), 2.response object ( res ), 3.next middleware function
used to modify req and res objects for tasks like parsing request bodies, adding response headers

Types of express middleware
Application level middleware app.use
Router level middleware router.use
Built-in middleware express.static,express.json,express.urlencoded
Error handling middleware app.use(err,req,res,next)
Thirdparty middleware bodyparser,cookieparser

API Authorisation-
client ----> username & password ---> server side(generates jwt token)---->stores on client local store
client makes req-->token set into header Authorisation Bearer Token--->if token matched with stored then gets res else error
JWT- json web token
header- algorithm used and token type
payload- name user and other
Signature- header,payload,and secret

Atomicity 
By this, we mean that either the entire transaction takes place at once or doesn’t happen at all. 
There is no midway i.e. transactions do not occur partially. Each transaction is considered as one unit and either runs 
to completion or is not executed at all. It involves the following two operations. 
—Abort: If a transaction aborts, changes made to database are not visible. 
—Commit: If a transaction commits, changes made are visible. 
Atomicity is also known as the ‘All or nothing rule’. 

Consistency 
This means that integrity constraints must be maintained so that the database is consistent before and after the transaction. 
It refers to the correctness of a database. Referring to the example above, 
The total amount before and after the transaction must be maintained.

Isolation 
This property ensures that multiple transactions can occur concurrently without leading to the inconsistency of database state. 
Transactions occur independently without interference. Changes occurring in a particular transaction will not be visible to any 
other transaction until that particular change in that transaction is written to memory or has been committed. This property ensures that 
the execution of transactions concurrently will result in a state that is equivalent to a state achieved these were executed serially in some order. 

Durability: 
This property ensures that once the transaction has completed execution, the updates and modifications to the database are 
stored in and written to disk and they persist even if a system failure occurs. These updates now become permanent and are stored 
in non-volatile memory. The effects of the transaction, thus, are never lost.

Js Data Types
String Number BigInt Boolean undefined null Symbol Objects Function, Array, Buffer

REST
REpresentational State Transfer is an architectural style that defines a set of constraints to be used for creating web services
HTML, XML, Image or JSON

arrow function 
shorter syntax for a function expression 
does not have its own this, arguments, super, or new.target. 
best suited for non-method functions
cannot be used as constructors.