This is you in a Coding interview. And this is
the dream job that you really want. If you don’t prepare data structures and algorithms, there’s
a good chance that you will be rejected. Now, I am no Love Guru when it comes to
relationships. But for coding interviews, I do have some expertise. And to crack all these interviews, the only course I have ever used is called Data Structures and Algorithms. And the best
part is that I did not master DSA sitting in a classroom of a fancy university.
I did it online, all by myself, because I have no Computer Science degree.
Today, I will share my entire journey in detail so that you don’t repeat the same mistakes
that I made when I was struggling with DSA.
Before we go too deep into how to
learn data structures and algorithms, we need to first understand what data structures
and algorithms means. Believe it or not, you might have already used data structures and
algorithms in your life. For example, I want you to remember the time when the meaning of every new
word was not available on Google and you had to use an actual physical dictionary to look up the meaning of
a word. To find a word, let’s say “programming”, you would open the dictionary in the middle and look at
the words that are there on that page. Let’s say you landed on a page with words starting
with “m”. You know that “m” comes before the “p” of programming. So, the word “programming”
must come after the page you just opened. So, you start looking for “programming” in the right
half of the dictionary. If you repeat this step multiple times, you will end up finding the
word programming.
The process or in other words, the algorithm that you just saw is called “Binary
Search''. And the way data is stored, which is “dictionary” in this case, is called a data
structure . Don’t confuse this “dictionary” with the data structure “dictionary” that we might have seen in Python because they are slightly different. But why does a Software Engineer even need
data structures and algorithms? Imagine that in the dictionary example I just gave you, someone
starts from the beginning and keeps flipping one page at a time to find the word
“programming” .
It will take them many minutes to find just this one word. With “binary
search”, you will find it in a matter of seconds. That’s the power of algorithms. Now imagine
that instead of giving you a dictionary where the words are neatly organized in alphabetical
order, I gave you a bag full of paper slips each containing a word and its meaning. How long do you think
it would take you to find the word “programming”? At least a few hours unless you are really lucky.
That’s the power of ‘Data Structures'.
I hope that this example makes you even more
excited about learning Data Structures and Algorithms.To make learning DSA easier for you,
I recommend that you learn at least one Object Oriented Programming language before you start
DSA. That’s because most online resources for DSA will be using an object oriented programming language.
You can pick any popular language like Java, Javascript, C++ or Python. If you already
have a language that you are comfortable with, you can continue with that. But if you don’t,
I recommend that you pick Python for DSA. That’s because Python is less verbose and you
can write code really fast in Python.
And in an interview, where you only have 45 minutes to
solve a question, this would be really helpful. Now that we have that out of the way, let's talk
about how I started my DSA journey. If you have seen any of my previous videos, you know that
I am a strong advocate for “Learning by Doing”. Unfortunately, for DSA, I don’t think there is
any good resource that you can jump into and start learning by doing. That’s because
DSA requires a good theoretical foundation before you can actually apply it to any problems.
That’s why, I took the online course route for DSA. I used this course called Algorithms by Princeton University on Coursera. This course is divided into 2 parts and is taught in Java. But if you are looking for a good DSA course in languages other
than Java, I do have some recommendations for you later in the video.
Professor Sedgewick, who
is one of the instructors of this course, is famous for taking the worst case space complexity
of Quicksort from big o of n to big o of logn in 5 extra lines of code. If you don’t know
what that means, don’t worry about it. The point I am trying to make here is that this course is
taught by the best of the best. The instructors of this course have seen many algorithms come and
go during their career.
Their book on Algorithms has been a bestseller since the 1980s. That’s why
instead of just saying: “here are data structures and algorithms that exist”, they are able to
provide a complete context of why a particular data structure or algorithm exists and when to use
it. And purely from a learning standpoint, this course make you fall in love with algorithms. I can not recommend this course enough. But there is one big issue when it comes to
learning DSA. Most people don’t know how much is enough and where to draw the line. And I
also made a same mistake here. This is the first of the 3 big mistakes I made on my journey. I will share the other 2 later in the video. The mistake I made was that I I ended up completing both algorithms 1 and algorithms 2. I realized it much later in my journey that I did not need full Algorithms 2 for coding interviews. If I could
go back in time, I would skip the entire Week 3 and everything after Week 4.
I am not saying that
these things are not useful, it’s just that they are rarely asked in the interviews. And even if
there is some uncommon question that uses them, you would be able to solve it if you follow what
we are going to discuss in the rest of the video. Anyway, if Java is not your primary
language and you want to use C++ instead, there’s this course by IBM that you can
use. If Python is your language of choice, you can use this free course by Google on
Udacity. This Udacity course might not be free in your country but it’s free in the US. All
the links will be in the description.
By the way, in case you are wondering, I do not
get paid anything if you use any of the resources I am recommending today. So, the only
way to support us is by subscribing. After finishing a course on DSA, you will
become very powerful. And you might start believing that you can bend the entire
universe to get that dream job. And that would be the second big mistake that I made.
I
applied for many jobs after completing DSA but it did not get me anywhere. That’s because
knowing all these different algorithms and actually applying them to a new problem
are very different things. Add the interview time limit of 45 minutes on top of that
and it suddenly starts looking like an impossible task. For those who are having a hard time
finding a job even after learning DSA, trust me, I have been in your place. Here is how I solved
this issue. I went to Leetcode and started solving some interview questions there. If you don’t
already know, Leetcode is pretty much the best resource out there to practice DSA questions. All the
questions are labeled easy medium or hard based on difficulty level. In the beginning, you might
not be able to solve medium or hard problems. So, stick to easy questions. And when easy problems
really become easy for you, move on to the mediums and so on. And when
mediums start feeling easy, you are ready for the coding interviews. If you want me to make
a full video on how to use Leetcode efficiently, let me know in the comments.
Another resource that
I would like to mention here is “Top 10 algorithms in interview questions” on GeeksforGeeks. If you
have done your Leetcoding well, you would already know most of the algorithms here. But, it’s still
a good place to revise what you have learnt. But before you start applying for jobs, it’s very
important to set your expectations right. The first few interviews are most likely going to be
a disaster.
And that’s perfectly fine. That’s why, I recommend that you don’t start by applying
to your dream companies in the beginning. Do some practice by applying for companies that
might not be your top choice. And once you are doing well there, move on to the ones
that you really desire. And always remember that rejections are part of the process.
Like
they say, there are two ways to walk in life. The first is to walk like you are the king of
the world. The second one is to walk like you don’t give a f**k who the king is. Choose the second
one and don’t let anyone’s opinion discourage you from working towards your goal. And
as always, we are here to support you. Before I forget, let me tell you the third
big mistake that I made.
I used to think that mastering DSA will make sure that I can crack
any software engineer interview. But in reality, DSA is not the endgame. You still need
to impress the hiring managers and crack the behavioral interviews. If you
want to know how to do that, you can watch this video at the top. My name is
Sahil and I will see you in the next one..