Google Coding Interview With A Facebook Software Engineer
ฝัง
- เผยแพร่เมื่อ 26 ก.ย. 2024
- In this video, I conduct a mock Google coding interview with a Facebook Software Engineer, SecondThread, who's also a competitive programmer. As a Google Software Engineer, I interviewed dozens of candidates. This is exactly the type of coding interview that you would get at Google, Facebook, or any other big tech company.
Check out @SecondThread's channel for cool competitive programming content: / @secondthread
AlgoExpert: www.algoexpert...
SystemsExpert: www.systemsexp...
My LinkedIn: / clementmihailescu
My Instagram: / clement_mihailescu
My Twitter: / clemmihai
Prepping for coding interviews or systems design interviews? Practice with hundreds of video explanations of popular interview questions and a full-fledged coding workspace on AlgoExpert - www.algoexpert.io - and use the promo code "clem" for a discount on the platform!
So?! Is David an absolute savage at algo problems or what?! Be sure to check out the Q&A interview I did with him here: th-cam.com/video/9ki1-xe6XzU/w-d-xo.html - as well as David’s TH-cam channel if you’re into competitive programming: th-cam.com/channels/XbCohpE9IoVQUD2Ifg1d1g.html
Thanks for the interesting and fun problem! I really enjoyed the opportunity to work on it!
If somebody does not know this Aho-corasick algorithm, then the time complexity will be O(phoneNumberLength^2) with trie? Is there any better way to do it?
why is the facebook software engineer wearing google's tee??
@@same0533 That was google code jam competition tees
@@OG_Scratch oh
dude be bussin out random algorithms that even the interviewer doesn’t know out here like “lemme use the ahoshinjinjutsu”
😂😂🤣🤣
😅 Panic mode ....
😂😂😂😂
ahhhhhhhhhhhhhhhh
😂😂😂💀
23 years of software development experience. I just feel the industry is getting to such a stage that you need 2 skill sets - One skill set for doing the job and one skill set to pass interviews!
Absolutely yes
@@jimmyadaro I just feel if it was a more mature industry, these interview processes would be more streamlined. Doctors and lawyers do not go through loops as they have a standard professional accredition. But in this industry as it is so new, you have to prove yourself over and over again. Past experience does not seem to count even if legitimate. The problem is unlike other professions, there is no real way to verify the experience.
Sumit you are a wise man and great comment I agree 1000% but add another thing landing on interview
before leetcode type of questions, there were whiteboard questions. I'd rather do LC type of questions than whiteboard questions.
that's true. An argument in favor of these interviews that I've heard is that big tech companies want to hire candidates who are so strong willed about joining the company that they will put in all the effort required for clearing these interviews.
These are cool but it'd really help my ego if you hosted a mock coding interview with a candidate struggling to remember how binary search works.
Nah deadass bro I'm right with you 😂😂😂😂😂😂😂😂😂
Hahahahaha
Actually tho seeing someone struggle a lot with an interview would be interesting but I don't think the brutal internet would be very nice about it
YES that's a great idea
Better yet a candidate that doesn't know what binary search is.
we can scare our interviewer by saying different algo names
The Corbomite Maneuver Algorithm gives O( log(log(n)) time. Runs quick for even international phone numbers
@@lolerskates876 ok lets go with that
@@lolerskates876Can you give me a link to that algo??
I found throwing out these jargons and technicals terms on interviewers face very effective in impressing the interviewer.
yeah!! LOL
Normal people: watching horror films and yelling at the characters to get out
Competitive programmers: watching coding interviews and yelling data structures at the interviewees
Lol I love this comment the most 🤣🤣
trie
🤣
I spend so much time going: why not a hash table?!
that's not just a facebook engineer, that is a competitive coder
Programming interview tip: disable spell check, auto correct, turn on mono space font
I think whats good to note is not the algorithm he used specifically but the part where he took the time to consider and evaluate different solutions before implementation.
For all those that watched this and feel stupid, remember David has spent 6 years coding and mentioned he used to do 40hrs a week with CP for his college years. So don't feel stupid, but do cry at the fact that it might take years to get this good.
I've been a developer for about 8 years and this video blew my mind 😂 there are levels to this shit
@@azz111full definitely agree I have 6 years of commercial experience and feel the question itself is quite ok, but the speed David types the code is absolutely insane and so it is really hard to follow.
thats why it's way more chilling to watch this when you haven't even started university (Yay I don't have to know all of this already xD)
what is CP?
competitive programming
24:03 that's me in every coding interview
😂😂😂
I am jobless
Nice one.
Good one😂
The easier solution is:
1. Reformat the strings to numbers.
2. Create suffix tree for the main number.
3. Check for each number if it is in the suffix tree.
That will take O(numOfStrings*LengthOfNumber) time.
O(numOfStrings + LengthOfNumber) space.
This would be much easier..
Yes that's way easier its some sought of rabin Karp
This problem looks similar to word break problem. Is this correct?
I solved it with a hashmap. Converted the input number to a hashmap with the count of each digit, and did the same for every test word in the list.
then you just compare the letter counts in both hashmaps to see if the test word can be created.
Wondering if he refers to neighboring node in a graph as "bro" :-)
🤣
Kids and bros :D
@@clem hello sir , can you please provide or suggest any source to learn data structures and algorithms from absolute beginner to master level .
Wow I learned so much, including that I'm never gonna get a job as a programmer :D
Most jobs are not this technical and algorithmic/data structure heavy. Your typical programming interview will probably not even do one of these challenges. Software engineers who have have been in development for many years probably cannot do this without a bit of training. This does not mean that the software engineer is not as good as the competitive programmer. In fact, being able to do these types of competitive programming questions does not even guarantee you to be a good developer. What's most important is your ability to understand and read code. Also, you need to understand what is being used in the industry and be familiar with frameworks. To land a job, what matters is that you understand the concepts and in the interview, what matters more than actually solving the problem, is HOW you solve the problem Break the problem down into little pieces and build upon it and don't forget to be inquisitive. Be disciplined in your studies and I am sure you'll be able to land a job
@@johnnycashcow1130 this is my fear. Next friday i have an interview for a programmer/tester position where i will get 1 python and 1 c++ question. C++ is good cause i did lots of embedded while in college, but havent touched python in years. I know it will be sthing simple like make a function that does sthing easy but am afraid that i am gonna get sthing like this
@@tnikoli40 how it went bro
Depends on the industry
@@tnikoli40 Bet they asked something like jane has apple in her basket and john has oranges in his. Calculate the distance of the sun to the moon and code how to use a rocket to get there.
I could be wrong, but after attempting this problem it's clear that you can also solve it (pretty quickly) by converting all of the input words into numbers (using a hashmap) and then checking if those numbers are contained in the phoneNumber input with a simple if "322" in "322245" check (for example). This gives you a space complexity of O(N = Lenght of Array) and time complexity of O(N*M) where M = Length of Word. I like the uploaded solution in this video a lot, but for many new grads and underclassmen looking for jobs who feel intimidated by this, then just know there's an equally valid and much simpler solution to this problem!
Thank you for this comment. Really. I was sweating and crying at this video
I thought the same thing!
I guess the "in" check is a bit slow because for it to check if first is on second, it has to go through all the second string untill it finds the coincidence (if there's one). And the method he proposed is usefull in the sense that it uses information gained with previous checks.
For example, we have "foo" and "foots" and we want to know if either of those are on "footage", if you do the "in" check for Both, the "foo" will be very fast while the "foots" one will take (the length of the word we're searching in) minus (the length of the word "foots"), with the method he proposed, after knowing that the coincidence "foo" appears on the word, we just gotta continue from there to find out that "foot" is in the word but then the coincidence breaks. So we just took two steps by using information gained with previous comparations.
Is like the "foreach word: If word in theThing" but where you're allowed to use information you gain with each new word, so that makes it a bit faster (and for large enough arrays, way more faster)
yes.
@@obsidian8037 but he had to build that aho thing which who knows what complexity its has (both time space) to populate all words. He never mentioned that.
@@dionisorules it runs in linear time, just bfs
I really wish in a real interview the interviewer would have allowed me to leave the hard portion of the implementation of the algorithm blank and to proceed with the rest of the bits and pieces of the program with the method signature intact 😂. You are awesome Clement! This would have made my life so much easier 😊.
12:45 honestly most impressed with him drawing out the trie in google docs, that's a skill in itself.
The speed was insane 😂
space bar go brrrrrr
@@mirsella6204 I think it goes like "tuk tuk tuktuktuk tuk"
Now I want to see clem being interviewed XD
Second thread is my idol.. I follow him a lot for competitive programming
Ive GOT to see this q&a video bc i am amazed how easily he walked thru all of this.
I regularly watch second threads TH-cam channel, but didn't know he was a facebook software engineer till now🔥
Same bruh
You should have checked his Facebook profile : p
i though he was a student.
@@ironyman7015 😂
I regularly watch SecondThread videos and I knew since long back that he recently started working for FACEBOOK APP and was also a tester for Facebook hackercup
Basically is a normal exercise. The lenght of the phone number is in the praxis fix, so that is possible to simplify the solution. You just convert the words in number, and you build all possible permutations with these numbers. If the combination have a match with the given nbr., you find then word combination.
#include
using namespace std;
// Ques: from a numpad given a number and a vector of string of words, find all the possible words that can be formed from the number
vector solve(string number, vector &words, unordered_map &numpad)
{
vector res;
for (auto it : words)
{
string temp = "";
for (int i = 0; i < it.length(); i++)
{
temp.append(numpad[it[i]]);
}
if (number.find(temp) != string ::npos)
{
res.push_back(it);
}
}
return res;
}
int main()
{
unordered_map numpad;
numpad['b'] = '2';
numpad['a'] = '2';
numpad['c'] = '2';
numpad['d'] = '3';
numpad['e'] = '3';
numpad['f'] = '3';
numpad['g'] = '4';
numpad['h'] = '4';
numpad['i'] = '4';
numpad['j'] = '5';
numpad['k'] = '5';
numpad['l'] = '5';
numpad['m'] = '6';
numpad['n'] = '6';
numpad['o'] = '6';
numpad['p'] = '7';
numpad['q'] = '7';
numpad['r'] = '7';
numpad['s'] = '7';
numpad['t'] = '8';
numpad['u'] = '8';
numpad['v'] = '8';
numpad['w'] = '9';
numpad['x'] = '9';
numpad['y'] = '9';
numpad['z'] = '9';
string number = "3662277";
vector words = {"foo", "bar", "baz", "foobar", "emo", "cap", "car", "cat"};
vector res = solve(number, words, numpad);
for (auto it : res)
{
cout
hi
I just studied for loops and came across this video. My self-esteem dropped to the ground. 😅
Most convoluted approach to solving a problem I have ever seen. XD
David is an absolute god not only with his quick solutions but his coherent ability to explain things very simply is awesome !!!
i assume ur experienced. why doesn't he just do
let number = "3662277";
let phonePad = ["", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"]
let words = ["foo", "bar", "baz", "foobar", "emo", "cap", "car", "cat"];
let works = [];
for(var a=0; a
@@warpromo6636 because 90% of Google, Facebook, Amazon interviewers are super anal about you giving an optimized solution using tree structures in 30 minutes that excuses without errors. ( they themselves wouldn't be able to do it, the irony). Which is why these interview methods are broken and outdated
That Guy is a Mathematician!
@clement, I love how you ask questions that's simple enough to solve within the timeframe but will get great signals out of the candidate. This will be testing people on their problem solving skills instead of how well they can prep for an exam.
Second thought is that it's pretty cringe following through his interview since my thought process is very much top down compare to David's bottom up. So it's very interesting to see how we have such polarize types of engineers.
He's a facebook engineer? I thought he was a competitive programmer student.
New grad, dope channel btw I watch you both.
It's me
u guys had me at the part where u were explaining how the words correspond to the numbers :D
Could you do one with a “typical” college student in college? Usually these people you interview are 1%er’s if that makes sense and it makes me as a computer scientist on my second year of college super intimidated and inferior.
But, to put it bluntly, that does nothing but make you feel better about your current situation in your career. Seeing a very competent Software Engineer tackle these problems helps you get a better understanding of how you should approach these interview problems.
Dont compare yourself to these guys expecting to be this good.. do it to give yourself something to strive for. Accept where you are and keep taking baby steps and before you know it youll be here
Just admire what people are able to do and strive to get better, thats all you need to do. Go your own path and don't chase after those guys.
I feel like I might’ve not gotten my point across. I want to have a “typical” college student/person do it so I know how exactly they would go about the interview because I haven’t seen how THEY would go about the problems. Because everyone that has taken these mock interviews already know how to do it (for the most part) and breeze through it like nothing. The closest person we’ve seen to a “typical” interview was Tech with Tim’s.
@@rousseau327 Sure, however, anyone soon to graduate and seek a new position are among the most likely demographic looking at these videos.
Pro tip: You can name drop Aho in an interview, but never call the interviewer Aho.
Ahh.... A man of culture I see XD
Lmaoo
You have to do a coding interview with the cherno he is SUPER SMART!!
How impressive he knows such algorithms, How can he not forget that haha 😂
when the interviewee brings out the big algorithms
David is a Great programmer!! he explains everything very nicely
Thanks, wish everyone else would realize this
Amazing... Really liked this one. Also, liked seeing some java.
Here's another GREAT vid on how to get into Google: th-cam.com/video/vqB_9eSaflg/w-d-xo.html
Instead of doing complex Aho-Corasik, we can do a lil tricky hashing stuff here.
Suppose N= all the characters in input.
We will map all the substrings we find from given number of length less or equal to √N to find matching in the strings size less than equal √N and for bigger strings we can manually hash match each with the given number string!
Complexity: N√N*(some log factor for mapping)
Damn dude, just go with the O(n^2) implementation and hard code the character to number conversion. There's no reason to worry about O(n^2) runtime when n is so small. If your code is simpler and takes less time to write, and isn't performance critical, it's more maintainable and easier to understand.
I was thinking about pre-calculating numbers ahead like every common word(s) (there is like 300k words in english), storing them with certain hash/bite-encode (idk how to explain aka shortcut) and then only regular binary search or something as B+ tree, so it would take time in pre-calculating phase but after it it has O(log2) space requirment is worse but it's price that you pay for fast search? I hope it makes sense a little :D
That is why you are not working at Google :D
@@Smoothie128 Hah, you're right :) I work at facebook instead.
@@slayemin dude stop you destroyed him
@@slayemin bruh, that's brutal 😂
Google Coding Interview With A Facebook Software Engineer who is wearing a Google T-Shirt! 😅
I can see the Facebook engineers adrenaline rush as he solves it, passion!! Reminds me of when clement is presenting in a video, passion!! Social cues like these are always so awesome to notice, Passion!! lol
Passion!!
LOL @ Clem's reaction when SecondThread says "Aho-Corasick" for the first time 😂
As a 18 year old with basics notions of programming, this makes me wanna spontaneously combust
For those who want a simple alternative solution I made using JavaScript, not as advanced as the solution in this video, not using any special algorithms (after I heard the question, I decided to attempt it first before continuing the video) but I believe easier to understand, I have added in reply of this comment so that I don't flood this comment section, copy paste into a js file and use node to run it! :)
If anyone have any comments that can help me improve on my code, do reply! I'm here to learn as well
Explanations of my code:
1. I used a lookup table (mapToNumber) because it's efficient and easy to understand, key value pair.
2. I used multiple functions to try to make the code as clean as possible
3. I made sure the functions in my code are pure functions (meaning return value is only determined by its input values)
4. I used split function to determine if word exists, basically, after the split function, the returned string will change if the number string exists in the phone number, by literally using the converted word to number as the delimiter. so, example if foo = '366', the program will find the string 366 in the phone number, and if it exists, it will modify the phone number, and a check will come in to determine if the string has changed.
Looking smart in this hair style sir. Also thank you for being such an inspiration person and thank you for helping us with your awesome videos
That was pretty complex😵. If I were asked this question by an interviewer in some companies interview I would have said like the best possible solution to this problem is not trying for this company at all...!!!😂
hahaha yeah... and for a simple phone number
He overcomplicates it though IMO, maybe because he wanted optimal complexity idk .
its not hard. You can solve it with a hash map . Its getting a super optimal sol that's hard
skill 100 %, code readability 100 %, communication 100%, you have nailed it 2nd tread, Google is knocking your door. : )
He probably doesn't want to switch. Every year he gets opportunity to set problems for mera Hackercup and commentate on it. Imagine getting paid to do what you love.
Google stopped all it's cp contests
David (aka second thread) completed his bachelor's degree in 2020.
And now he is full time Engineer i think
Indeed, I'm surprised you know!
@@SecondThread yeah.. from linkedin
I always like Clement’s devious smirk when he hears that they’re close
cool! I actually came up with like 75% of the solution before seeing what he did. I was stuck at figuring out how to backtrack back once you've explored a path, and I guess there was a fancy algorithm (aho) that finds the fail links. In a real interview, I guess leaving out the aho algorithm would be ok as long as you were able to mention and talk about it.
Where do you work
I already have a job in programming but watching this still makes me shit my pants.... I'm very far from his level
I don't have a job bro I am from india.
@@aj9706 I am laughing at all you people! reading the comments like i know everything! i don't know why LMAO
Converting the array of words to equivalent number strings.. and then iterate each string and check phoneNumber.indexOf(str) != -1 to insert it to the output array.
Geat sir
So glad I'm working in small companies, don't deal with interviews like this and earn even better money
Tbh this could have been done in such a simple way. I dont understand why ppl dont simply use arraylist/maps and existing built in datastructures, which already have utility methods that make our life so much easier..
None the less nice problem
I would have used an arraylist here however I'm not sure how to compute the space time complexity. So maybe they're after the lowest time complexity here.
Clement be like, "I know you work in a cool company but let's see if you're eligible to work at another cool company!" 😂
Petition for Clement to add this question on algoexpert
After watching 30 mins I can't even under the question 😅😅🤣😂
I don't know why but i like the way this guy talks and explains things
I enjoy the format of these interviews and I’m curious if you as the interviewer, would be open to redefining the approach to attacking this toward a solution. If you or others would generally be open to allowing the interviewee basically change the use case to begin with the end defining the beginning. If your eyes haven’t glazed over yet, what I mean in this situation is to try and convince the interviewer up front; agree on an assumption which would reduce complexity. I realize you’re looking for construction ability, complexity, quality, efficiency, but if you could agree ahead of time on a logic-based route to completion, before coding begins, then I would say I would provide the customer all the available phone number combinations they could choose from, as the output and ask them to enter their word since they’ve probably settled on a company name and just need to find a number that can represent the name.
Not targeting this instance in particular but I guess I am. Overall, would this taint the interview or would this generally be thought of positively, a perspective employee pushing back a bit right up front. I know for me, I try to dumb the complexity down (for lack of a better phrase), so I can begin with what feels like my idea or my internal translation of the ask. Thanks and sorry if I’ve bored everyone with my question.
Would love to hear Clement's answer to this question as this very situation happens... essentially with every project in software design and consulting.
I don't actually do that much algorithms and data structures but I looked at two videos Clement and I solved both of them in between 1-2 hours. Its not really hard for me even tho I have only 2 years of experience. I will admit that I make a lot of mistakes and I might not be that much articulate and explain things that I am doing in such clear way that those engineers do. When you first watch video you say these guys are super genius or that kind of but when you actually do them it really is easy. I hope I will keep up doing algorighms for a week I really enjoyed those problems.
watching this, i don't know if i can ever be this good
Why not?
It's a really bad habit to compare yourself to others. David is "this good" because he focuses his attention on learning and teaching rather than doubting his ability. You should watch this and feel inspired to learn!
you know, im so so happy when i created login form (not reaponsive) with simple html and css.
if i compared myself to this guys, im nothing, but remember, there are people below you cant do things you do right now..
but im still hoping that i can be as good as this guys, i wont compare myself tho, but i learn from them..
Analogy:
If you never learned how to ride a bicycle, the beginning of you deciding to ride one will be rough and make you wonder how is it even possible to have such control/balance on that 2 wheels thing!
But if you perceiver you will eventually get to a point where you start getting it right because it's not magic but rather all about adaptation.
They practiced years for this kind of stuff and all they do afterwards is pattern matching and reuse the knowledge they already have. Mostly they lack some other concepts in CS.
So don't think like that, just start solving some problems on yout own and you will see that it will get easier and easier.
Thank you Clement the video helped in giving an overview of how to communicate our ideas during an interview
The solution I had was-
1. A Map to store letter, numeric pair. Total keys 26.
2. Take a word, convert it to numeric equivalent value.
3. Check if phone number string contains this equivalent value.
I think this is a simpler approach.
well this is not javascript it depends on which language you use. regardless he thinks on the spot and he has very good ability to communicate his thoughts which is the difference why he works at places like google, (in his case, facebook) and other people like on here, who "brag" that they can do it in much better way...but cant land a job at Starbucks because, can't speak their name properly ;/
@@milovanmilovanov2598 @Milovan Milovanov Did you see that I started the comment with "The solution I had", this was in no way demeaning to anyone and let alone you. I don't get why you got triggered and basically started ranting about stuff. Btw I did try it and when I got it, only then I posted this comment. Well your comment was distasteful here. On the name comment, please choose to accept people with different backgrounds and places trying to make the best softwares available.
I was thinking of something like this, too, but I'm thinking in python terms here. His solution is in my eyes - though appearing unnecessarily complex - actually much more elegant, as he does not check the words one by one, but all of them at once. Using a BFS here to navigate the graph of failure edges provides a major advantage when it comes to datasets much larger than the ones used for example here, as you basically build a "frontier" moving through the graph. It gathers much more results in one go.
Yeah, but it had to be faster. He reduced complexity. Nice job by the way 👍
Knuth-Morris-Pratt algorithm is the key of succes
Hey Clement, do you have a front end expert in the works? I would totally buy that!
The most delightful coding editor out there -- google docs.... lolllllllll
What about using /10 and % length of the converted word? Then you can subtract the two numbers if the result is zero you've found it. Would be O(n*#words).
Top solution! Much better than algorithm which was implemented in video!
Aho-jurassicpark wtf. This dude just out here spitting theorems
Simple solution is to make a hash from letter to number.
Use hash to generate string
Use regex number match hash(letters)
Complexity is less than (number length)*list converted
Where the conversion is average word length times number of words
You should try running the code to see if it actually works. This is one of the problems with these whiteboard exams. And you should have him comment his code too.
Did I miss why this wasn't implemented with just a string.Contains() call?
it's slower to do it this way
It’s easy but very understandable explanation.
Please try to call gennady korotkevich on your channel for these kind of google interview.. It will be fun to see how he see these interviews..
Watch his live streams instead!
His solution's r just out of the box! I dont even dare to look at his code!!🙄
Done is 16 lines of code. How does it compare for an interview? (python) :
def MatchChecker(words, phone_number):
letters_in_num = ('', 'ABC', 'DEF', 'GHI', 'JKL', 'MNO', 'PQRS', 'TUV', 'WXYZ')
match = []
for i in range(len(words)):
tester = ''
for j in range(len(words[i])):
word = words[i].upper()
for k in range(len(letters_in_num)):
if word[j] in letters_in_num[k]:
tester += str(k+1)
match.append(tester)
for i in range(len(match)):
if match[i] in phone_number:
print(words[i])
That was cool
WHAT ARE YOU DOING HERE LOL?
@@peepoHappyy if you have watched my videos, and looking my comments in this geeky thing. Then I can imagine why would you be amused. Can I ask. Is it that the case? That would be awesome😂
@@Clashtoons Man, I mean you make cartoons and such, why are you on a video about a coding interview?? 😂
Also, your cartoons are one of my pure nostalgia. Keep up the amazing work!
@@peepoHappyy I make cartoons as an hobby and do coding also as an hobby and a profession. Thank you. This is the first time me being "recognised in public" moment for me.
I'm not sure why it became so complicated when the problem is actually simple. Considering we have a constant of int=>['letters'] and then compare if the phonenumber(input) has it in the string.
->convert to int using the constants 1=a,b,c etc
->loop through the array of string
->substring to phonenumber
-> true or false.
Well I'm also confused as to why it had to be so complicated. I don't even think you have a worse complexity with your solution.
Given the inputs probably change every time, building that aho table is way more expensive than just doing a string.Sub()...
Going directly for a complicated algorithm is seldom recommended. Usually data is small and a simple and straightforward solution works fine. In this case, the phone number can be expected to be relatively short, not more than 20 digits. The words will also be short. But the number of words might be large. Therefore, it's probably okay if the algorithm is O(N²) in the length of the phone number, but it should be O(N) in the number of words.
i want back my educational round explanations
This is such a good question. I wish i was smart enough to be able to look at something and come up with n number of algos off the top of my head that would be a candidate for it. Love your interviews.
you can be that smart! You just have to surround yourself this sort of content and build up a knowledge base. look at his github repo at 47:49. When he hears about an algorithm, he does some research on it, then tries to implement it himself, then saves it in his collection. Always be curious and willing to try new things, you'd be amazed at what you can accomplish.
FINALLY ONE JAVA CODER
Programmer guy was like “chock on that”
oh man, the excitement I get every time I see the notification that clement uploaded a new video
That was fun. But in real interview this can be a really dangerous strategy, because interviewer must be ready for such turn of events. And Clément pointed that out, thanks.
JavaScript can do this very quickly with built-in functions.
Step 1, create an object (which is searchable) that has each letter mapped to a corresponding digit.
For example:
var digits = {};
digits.a = 2;
digits.b = 2;
digits.c = 2;
digits.d = 3;
...
Step 2, simple for loop that converts words in given input array to numerical representation:
for (var word in words) {
numbers.push(words[word]
.split("").map(function(item) {
return digits[item]
}).join(""));
}
Step 3, return result by using "includes" function and filtering out nulls from the map:
result = numbers.map(function(item, index) {
if (phoneNumber.includes(item)) {
return words[index];
}
}).filter(function(item) {
return item !== undefined;
});
return result;
While my solution may not be the fastest, given the easy readability and maintainability of the resulting code, I would opt for that solution over a more esoteric node approach. Just my 2 cents!
Nein
My approach to answering this question would be to tell the interviewer to get off my back, like way off it. Then I'd type out random gibberish in latin like loren ipsum hoping the interviewer would be impressed. If he isnt then I'd tell him he better be because it's voodoo and he's cursed if he doesn't give me my job. Then I'd walk out.
Bold of you to think it is already YOUR Job 😁
Why not just do a KMP? The time complexity for KMP is linear. Straight forward solution could be go through each word, use kmp to figure out if it is included in the given phone number.
you will kmp with the main string multiple times, so you get n*m
aho corasic allows us to only pass through the main string once. giving n+m.
Well, translating the words into string of digits, loop for every digits string, if the digit string is contained in telephone number as a string of digits (first occurrence) return word is contained otherwise word is not contained... there are many methods to compare two strings, and we're not going to re-engineering the wheel... To further optimize, you can momoize the function that check if the "numerical" string is inside the telephone number.
Great to see you are sticking to primitive int arrays instead of Arraylist
Towards the end you used ArrayDeque which might upset interviwers who dont have java background.
this is perfect timing because i had to implement aho-corasick for work last week!!!!
What kind of work do you do? Lmao
@@Garentei i am an nlp engineer and implmenting/designing fast text search is part of daily work lol so this kind of stuff comes up very often. i deal with graphs and trees daily lol
@@skdx1000 Cool!
Someone like clément can only put ad of his own company in his video.
Thanks for posting this problem. Very interesting. I would have never tried to apply some algorithm to this solution, however (maybe that's why I don't work for google or facebook, lol).
I came up with a solution in C# using a Dictionary and 1 line of LINQ code. Simplicity almost always trumps complexity. My advice would be to use whatever libraries are available before resorting to some hand-coded algorithm for someone else to maintain - only resort to hand-coding when performance is an issue.
Yea I was thinking of just converting words to numbers and then doing string.contains on each.
Complexity can often trump complexity for high performance applications.
I'm learning Python and programming for 6 months now and i found the/a solution. Not sure that its nice or clean or "pythonic", and i still have a long road ahead. But I'm so happy and it's a great feeling ^^
*Facts about clement*
Everyone: He worked at google and Facebook.
Me: He has a secret Black V-Neck shirt collection
I have had this problem on a coding challenge but on steroids (list of phone numbers and list of strings, and then return them in an ordered list) basically the hard part was to get it done with an acceptable runtime
what im actually worried about is: this is the type of questions a fresh graduate student will face in interviews? Or what exactly am facing
No, in fact, what you see here is a simple version of the question. People usually see harder questions.
This is what separates us Real developers from the Kid developers.
Question! Maybe I didn't understand the problem. He gave the solution at minute 5:00, so why didn't go with this simple solution instead to go through this more complex solution? (like loop the array of words converted in numbers and use the "contain" function to see if is contained in the phone number) Thanks and sorry for don't understand :S
Pretty cool that he implemented the hard algorithm I hadn't seen that one on a while but I think other commentators are correct to point out that the interview process has gone out of control but I like this particular problem because imo Dave is a bit too smart for his own good here, an experienced software engineer would have come up with a much faster solution which happens to be the naive one with a few bells and whistles:
two digits can comfortably fit in a byte so 15 digits can fit in 8 bytes which a modern processor can compare in one instruction. Encoding the phone number and the words into 32bit integers and then carefully shifting and comparing is extremely efficient on modern hardware. On the other hand trie traversals cripple speculative execution and the ROB usage, modern CPUs hate hierarchical data structures (or more precisely they love simple ones).
In this particular problem we would probably not have too much of a cache miss/page fault problem but generally that is another important concern with hierarchical datastructures.
I guess there is some important advice to be extracted here: asymptotic complexity virtually always lies. If we were dealing with platonic Turing machines maybe it would be important but taking advantage of the actual material conditions of the problem is what imo makes a _really_ good engineer.
Yes, convert to BCD then compare to precompute patterns for the most popular in the distribution. For the rest do something akin to brute force. Then hire a mathematician to chime in on its big O or just observe it blow the doors off whatever's going on here.
This guy is so in the zone he didn’t even realize clement was choking 😆 24:12
This the kind of concentration you need bruh
He turned off mic probably
David is a beast at coding. How wrong would I be if I said I'd just check for substrings in the original phonenumber after converting the words to numbers? Lol
I paused the video when the problem was announced and tried to come up with a whiteboard solution. And this is exactly what I want to know.
@@self.medicate It's not too hard to do. I did a mathsy version that essential does "substring" type comparison. It's fast and much simpler than the ones used and described in the interview. You can find my code here: gist.github.com/AndrewWCarson/16150020cf65acc0ab35686dec005746
@@AndrewWCarson actual comment from your code: “this line is very smart”
r/iamverysmart vibes lol
This just gave me anxiety about my upcoming interview at google😮