This is why you are FAILING at Interviews

Hi,

Here is another video from my side: "This is why you are failing at Coding Interviews"

If you have not subscribed to my YouTube channel, now is the right time as its all about making you ready to get your dream job. I share tips, lectures(like dp, dp on trees, graphs, squareroot decomposition), and the right mindset needed to crack coding interviews.

Rachit, an IIT Roorkee Alumnus and Software Engineer at Microsoft shares the major issues that people overlook while they are failing at Coding Interviews, despite being good at technical skills.

Subscribe to see more of me. Let me know if this helped. Go get a job at your dream company!

Cheers!

If you are preparing for Coding Interviews, WATCH THIS!

Hi,

Here is another video from my side: "If you are preparing for Coding Interviews, WATCH THIS!"

If you have not subscribed to my YouTube channel, now is the right time as its all about making you ready to get your dream job. I share tips, lectures(like dp, dp on trees, graphs, squareroot decomposition), and the right mindset needed to crack coding interviews.

In this video, I share what is the story behind the present hiring process for companies like Microsoft, Amazon, Goldman Sachs and then I share what are the various topics you need to study to prepare for them.

Subscribe to see more of me. Let me know if this helped. Go get a job at your dream company!

Cheers!

How to excel at Competitive Programming | ft. FFAO from Codeforces

Hi guys! ✋

rachit jain blog, Rachit Jain, rachit jain iit roorkee, rachit jain iitr, rachit iitr,rachit codechef, rachit hackerrank, rachit jain microsoft

I got the opportunity to talk to one of my favorite coders. I remember I used to read comments by ffao and just see how great his rating curve is and how soon he came red on Codeforces.

So I made a video on YouTube where ffao answered a lot many questions about competitive programming and how one can excel in this field.

My screencast software got some issues and we got a poor video quality and I sincerely apologize to ffao and the audience.

I can't ask ffao the time to again record with me, and I was almost sure of not uploading the video. But the audio is great, and I decided to have it on my YouTube channel. 

You can watch the video here.

You can also refer this blog post to have a summary of what we discussed in the video.

• What's your educational background?
• ffao: I have a five-year bachelor’s degree in Computer Engineering from Instituto Tecnológico de Aeronáutica (ITA), a Brazilian university

• When did you start programming?
• ffao: I wrote my first program when I was 13, as with a lot of people that happened because I really liked video games and wanted to know more about making them (spoiler: turns out it’s actually quite time-consuming). At that point I could only make very simple programs, like “type in a number and the program tells you if it’s even or not”, but I picked up more as I went along.

• Why does math background help?
• ffao: I can’t even pinpoint where the math ends and the programming starts! Functions, recursive relations, geometry, transforming algebraic expressions – these are all things you do routinely in math and these are all things you do routinely in competitive programming. Just as math helped me with programming, studying for programming also helped me do better at math, so these things are quite tightly coupled.

• Should students prefer math over computer science for graduation?
• ffao: There isn’t an objectively correct answer to this question – graduation choice should be influenced by the student’s tastes and what they intend to do with their life, so my best advice would be to research what graduates at each of these fields tend to do and go towards the one that has the choices that appeal to you the most. Getting into a programming job in general is easier with a computer science degree, but I have heard of jobs that hire mathematicians due to their usual analytical skills.

• Can you relate your success in programming to your childhood?
• ffao: Sure, I believe everyone’s experiences in their whole life matter - I’ve always liked math, so I didn’t have trouble with those parts. I also did a bit of programming, so I did not have to struggle with learning what ifs and whiles do since I already struggled with it before.

• How can intermediate coders excel and reach the next target?
• ffao: Just keep at it – do every competition you can, and you’ll struggle with a problem or two; those should be the problems a bit above your skill level so make sure you understand why you couldn’t solve the problem you couldn’t solve. Could you have approached the problem in a different way to get to the solution faster? Is there a technique you can generalize to solve a class of similar problems if they show up?

Other Questions that students requested:

• How to understand hard and tough concepts easily for example FFT , centroid decomposition etc.
• ffao: This sounds like the wrong question to ask. To be honest, FFT/centroid are not that useful and I didn’t learn about them for a very long time (I think I only knew about those things for a few months?) The best thing is to just go doing full competitions, without trying to learn specific techniques, until one of them comes up. But if you really want to know, my generic way to learn things when they do come up is: look up an explanation from someone who knows the subject well (there are a lot of bad tutorials, so you might have to search a lot to find a good one), try to do the most basic possible thing with the technique, then solve a few problems to see potential alternative ways to use it, then go back to solving random problems until it comes up naturally again.

• How to select problems for practice? Ladders in A2OJ sort problems by tag and number of submissions which are not that great.
• ffao: If you are training for a certain competition A, an obvious choice is to do previous editions of that competition for training. There are a lot of ICPC Regionals available online, also other competitions with quality problems like topcoder and codeforces. There isn’t a perfect answer to this and you’ll eventually find problems that are not helpful, the important thing is just to keep at it and eventually you’ll come across something interesting. I went to the Google Code Jam finals in 2014 and another finalist asked me how to find good problems, so I guess none of us really know. 😊

• Tackling DP and understanding the states to be defined and how this though process goes inside his head so rapidly.!
• What ffao said is exactly told in one of my videos to Introduction to Dynamic Programming that you can watch here.

Dynamic Programming: How to think of states?

If you liked the video, please hit the like button 👍, subscribe and share the videos among your college :D  

Have a good day! 😆

[Tutorial] SquareRoot Decomposition + Dynamic Programming in Competitive Programming

Hi guys! ✋

rachit jain blog, Rachit Jain, rachit jain iit roorkee, rachit jain iitr, rachit iitr,rachit codechef, rachit hackerrank, rachit jain microsoft

You are going to learn how Square Root Decomposition and DP can be mixed to generate harder problems.

This is an awesome math problem on Matrices. It is based on DP + Data Structures(Fenwick Tree/SquareRoot Decomposition). Its a counting problem from CSAcademy Junior Challenge 2017.

Problem Link is here.   

You are given a matrix $M$ with $N,M( \le 2000)$ rows and columns, and you have to count the no of special square submatrices. A square matrix is special if it has all $1s$ on its borders and principal diagonal(top-left to bottom-right). The rest of the matrix can be filled with either $0s$ and $1s$.  

In beginning, the problem seems to be solvable using only DP, but the solution is simply mind-blowing, jaw-dropping and beautiful.  

The trick here is to iterate on diagonals which are $O(N+M)$ in number. Then for each diagonal, count the number of special square submatrices that lie on current diaognal i.e their principal diagonal lies on the current diagonal that we are iterating. 

Lets pick any two points on the diagonal that we are currently at. 

Using DP, we do some preprocessing. Then the question is transformed to given two arrays $L,R$, find the number of pairs $(i, j)$ such that following 3 conditions are met:   

1. $i\le j$ 

2. $L_j \le i$

3. $R_i \ge j$  

We iterate on $j$, and use square root decomposition to solve this problem :)

The video tutorial is divided into 2 parts: 

1. Part1: Approaching the problem and building our solution

2. Part2: The Square Root Decomposition part

Refer the Video Description to find the links to problem link and other relevant information.

If you liked my efforts, please hit the like button 👍, subscribe and share the videos among your college :D  

Have a good day! 😆

An Interesting Math + Data Structure Problem from Codeforces (Round #430)

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rachit jain blog, Rachit Jain, rachit jain iit roorkee, rachit jain iitr, rachit iitr,rachit codechef, rachit hackerrank, rachit jain microsoft

This is a data structure(TRIE) + math based problem from Codeforces Round #430.
Problem Link is here.   
You are given an array $A$ of size $N$, and you have to perform $M$ operations on it.  
In each operation, you are given an integer $x$, and you perform XOR operation of every element of the array with $x$. Note that the array is updated after every operation and subsequent operations are performed on modified array. At end of every operation, you need to print the mex value of the updated array.     

NOTE: mex of a set $A$ is the least whole number ( $\ge 0$ ) which is not present in $A$.    

Check out the following video where I've described the solution:
CodeForces Round 430 - Problem D Tutorial (Number Theory, Trie)

Refer the Video Description to find the links to source code and problem link.

If you liked my efforts, please hit the like button 👍, subscribe and share the videos among your college :D  

Have a good day! 😆

An Interesting Number Theory Problem from CSAcademy(Round #43)

Hi guys! ✋

rachit jain blog, Rachit Jain, rachit jain iit roorkee, rachit jain iitr, rachit iitr,rachit codechef, rachit hackerrank, rachit jain microsoft

This is a greedy, math problem from CSAcademy Round #43.
You are given two integers $N,K$ and you are required to print an array of $N$ distinct integers $<10^6$ such that there are exactly $K$ pairs $(a[i], a[j])$ with their gcd as $1$.  

Check out the following video where I've described the solution:
CSAcademy Round 43 - Coprime Pairs Tutorial (Number Theory)

Refer the Video Description to find the links to source code and problem link.

The family 💓 has grown to 600+ subscribers and I thank you guys for the love and support :)  

If you liked my efforts, please hit the like button 👍, subscribe and share the videos among your college :D  

Have a good day! 😆

YouTube Playlist for Dynamic Programming

Hi guys! ✋

rachit jain blog, Rachit Jain, rachit jain iit roorkee, rachit jain iitr, rachit iitr,rachit codechef, rachit hackerrank, rachit jain microsoft

I am happy to launch the YouTube playlist for Dynamic Programming: From Zero to Hero.    

I've put in a lot of my efforts this time, kept the video detailed so that a lot of people (beginners for sure) are able to understand:
1. How to approach problems based on Dynamic Programming?
2. How to think of DP states?
3. How to build the DP recurrence relations?
4. Can DP problem be solved faster using MATRIX EXPONENTIATION? ✌

Beginners will surely learn a lot, lot, lot from this. 

Check out the following videos:
1. Intro to DP: How to approach DP states, Recurrences 
2. Dynamic Programming + Matrix Exponentiation

Check the Video Description to find the links to source code and problem link.

Finally, the family 💓 has grown to 500+ subscribers and I thank you guys for the love and support :)  

If you liked my efforts, please hit the like button 👍, subscribe and share the videos among your college :D  

Have a good day! 😆