Longest Common Prefix (LeetCode 14) | Full solution with animations and examples | Study Algorithms

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Most of the string based problems either revolve around a prefix or a suffix. A prefix is a character or a sequence of characters that occur in the beginning of a string. In this problem we try to find the longest common prefix in an array of strings. We first explore a naive and straight forward approach and then find an optimal solution using a neat little trick called sorting. Watch the video to learn how it makes the problem super easy to solve. All of this along with a dry-run of code in JAVA.
Chapters:
00:00 - Intro
01:03 - Problem statement and description
04:05 - Brute Force Method
07:10 - Efficient/Optimal solution
12:07 - Dry-run of Code
14:21 - Final Thoughts
Actual problem on LeetCode: leetcode.com/problems/longest...
📚 Links to topics I talk about in the video:
Brute Force Paradigm: • Brute Force algorithms...
Problems on Strings: • Strings
Quick Sort Algorithm: • Quick Sort super easy ...
Recursion based algorithm: • Recursion paradigms wi...
What is Big O?: • Big O Notation Simplif...
📘 A text based explanation is available at: studyalgorithms.com
Code on Github: github.com/nikoo28/java-solut...
Test-cases on Github: github.com/nikoo28/java-solut...
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#leetcode #programming #interview

[@dhritiarora4147]

All the 15 mins were worth it. Great job!

[@nikoo28]

Thanks for the support and motivation

[@user-kg6gu7re2w]

You always provide the best, easiest, and simplest approaches. I watch your explanations and then try to write the code independently, and I succeed most of the time. Keep making such great content. It really helps us a lot.

[@nikoo28]

that is so nice to hear. I hope to keep bringing quality content for you guys.

[@quantisticnumbers2633]

Definitely one of the easiest and best solutions that I came across. Thanks for the video!

[@englishpopop7694]

this breakdown made things much more clear and easy to comprehend

[@candichiu7850]

Thank you! The BEST on KZbin. Super explanation.Keep up the great work.

[@sumanthpai4587]

Very Articulately explained . with proper animations etc , really good job

[@tashi7316]

So far one of the best solution I have seen

[@CostaKazistov]

Great style of teaching algorithms. 10/10 👍

[@subhamagarwal476]

addicted to your channel. You explain so simple and in easy way. Thanks a lot

[@enriquegrageda]

My bro, you are a great teacher!

[@himadripaul7332]

excellent this channel will grow gradually ..no bakwas straight forward explanation ..

[@HY-eu4ei]

tried a lot of videos and i would say this was the best explanation of all such a easy and elaborative explanation. thank you

[@nikoo28]

Glad you feel this way ♥️

[@egm5081]

man, what amazing explanation, thank you so much!

[@saiyamjain6099]

Excellent explanation 🔥 keep making more videos loved it

[@kunalkheeva]

your videos seem like bit longer, but its really very productive, I couldnot even skip it for a sec, just great work!! Thank you!

[@nikoo28]

I really try to go over the concept, rather than just giving away the code...the same you would be solving a problem in an interview. Thanks for your support. Much appreciated. 😄

[@nginx.h]

bro i stuck at this problem and i dont understand how to solve this question but after watching some video i not getting it better but u solve this question with very simple approach. 👍👍 well done bro

[@shivenderkumar4521]

Very Simple and clear explaination , Thank you ❤

[@gopro12378]

Crystal clear concept thank you sir!

[@raghavkaushal7561]

Thank you so much brother!!! Your explanation is extremely simple to understand and follow. Wish I had a teacher like you.

[@kirankutte7073]

Awesome explaination. I liked the slow and animated explainartion. Good job!

[@nikoo28]

Glad you liked it

[@user-ig2kt4jp8i]

You're such a good teacher. Thank you!

[@nikoo28]

Glad you think so!

[@sharcodes]

Love your Solution. Best Wishes for You. I Would Love to see your Channel Grow, why this is so Underrated.

[@nikoo28]

Thanks for your support and motivation. I really hope the youtube algorithm picks up the channel soon 😅

[@PankajYadav-nz4gn]

Oh My GOD!!! I can't imagine that someone can be this good in explanation. Amazing and super thanks.

[@nikoo28]

Wow, thanks!

[@aparna5778]

Thanks for the explanation. Was easy to follow.

[@satyamgupta6030]

great teaching bhaiya. I always look for ur videos whenever I search for a solution of a leetcode question. No one comes close to you when it comes to explaining multiple approaches and finally solving with the most optimal approach . Thanks bhaiya.

[@nikoo28]

It's my pleasure

[@d54nirajthakare69]

The level of Explanation I saw today was amazing !!!

[@nikoo28]

So happy you felt that way

[@aradhyashukla2813]

Explained a complex problem very easily 💯👏

[@Prince-fv8mb]

loved the way you explained sir.....This channel is highly underrated

[@nikoo28]

Thanks for your support and motivation. I really hope the youtube algorithm picks up the channel soon 😅

[@animationTip]

I love the way of explanation.Thank u so much making such a video bhaiya .

[@eyerahulk]

Nice explanation, thanks man.

[@vm1662]

Great explanation! Thank you. :)

[@nickjr9994]

Very good explanation brother. This solution was so precise and easy to understand. Thanks a ton

[@nikoo28]

glad you liked it.

[@parulsaraogi6770]

Woww explained so well.. just loved it 🥰❤️

[@punamroy6639]

great explaination. Thank you

[@salmarafiq7695]

Amazing explanation!!!

[@curiousvaita]

Amazing Solution. Thanks a lot.

[@mdrabby1259]

Very good explanation ❤😊

[@ChaitanyaPimparkar]

keep them coming

[@AvinashKumar-ps4tw]

Very Crisp and interesting explanation

[@colveness9155]

ty for video, great explanation!

[@niteshpandey8207]

Esko dekh ye pta chala ki aise bhi question solve kr sakte hai.... keep posting

[@nikoo28]

😄

[@amitarajput1153]

Best Teacher. Please upload more videos. Super thanks

[@abhijitbiradar]

very nicely explained. thanks

[@PranitKothari]

You explain nicely!

[@LuckyAndDad]

Excellent narration

[@SMARTRIXDbztttmods]

*Excellent Work 🔥Thanks Sir*

[@AmeyBhogaonkar-vy2bx]

Worth it !!

[@SaumyaSharma007]

Thank you brother 🙌

[@karthikarthick5192]

great one bro keep making more and more u make learning so damn easy

[@chakri2622]

this video made to subscriber to never loss hope and don't give up u will grow

[@voidcrs]

This is a great solution.

[@palashbharati8818]

string longestCommonPrefix(vector& strs) { sort(strs.begin(), strs.end()); string st=strs[0], end=strs[strs.size()-1]; string ans; for(int i=0;i

[@oncloudnine4334]

bro can you explain why we go with first and last and explain why can't we go with first and second string

[@gauravsharma4994]

Man that was awesome

[@atishyadavit1036]

Amazing!!!!

[@anshikagarg9485]

I can't think... Thanku for this optimal approch

[@TemuriChitashvili]

Really good.😉

[@md.shimul4805]

Thank you so much!!!

[@simo_the_goat]

nice job

[@khushaldodeja8267]

Thankyou soo much buddy ❤️

[@rishabhjain7651]

love to way of explaination 😍

[@siddhigolatkar8558]

Thank you

[@kateach8056]

Thanks for solution.

[@DalisYn]

Thank you so much this one was a bit confusing

[@Chhooso]

Finally was able to understand it😭👍

[@erenyeager4452]

Hey, found a similar problem but no one had a good solution online. The idea is to find the longest palindromic prefix. Would help a lot if you can make a video on this. thanks for the videos. love them.

[@zack176]

Wow so you are finally tired of destroying world

[@spongebobsquarepants4576]

Interesting solution with sorting - but then you get n*log n. You can simply search the list for the shortest word and then compare it with all other words, thus making it O(n * k) where k is the length of the shortest word. Depending on the input you have in a real life scenario, your approach might be more efficient if the strings are very long, so if the length of the shoertest string k > n where n is number of values in the list, then your approach is more efficient. Anyway cool explanation thanks!

[@salmarafiq7695]

Sooooo goood:⁠-⁠) keep going 👏

[@huquea]

OMG, you took teaching algorithm to next level

[@nikoo28]

So happy you feel this way 😄

[@anshikagarg9485]

Awesome👍👍

[@kamleshkumarsingh5140]

SC will be O(n) right for using stringbuilder?? Great explanation though

[@nikoo28]

you are absolutely correct. My bad..the space complexity will be O(n)

[@hemant8762]

Thank you so much sir

[@bivashroy2829]

If the string contain a mixture of capital and small letter then sorting can't be the solution... string commonPrefix(vector& strs,int n){ string s1 = strs[0]; int ans_length = s1.length(); for(int i = 0 ; i< n ; i++){ int j = 0 ; while(j

[@debasmitadash9974]

You are amazing. ❤

[@nikoo28]

You're the best!

[@subee128]

Thank you very much

[@nikoo28]

Any time

[@mohdsameer2445]

very nicely explained bro

[@nikoo28]

🤝

[@ahmedabdul9137]

What is the time complexity of the brute force approach?

[@B_Drive_2K]

Nice Solution

[@kaustavhalder7263]

wow what an explanation

[@sarthakbhargava3514]

Thanks

[@kidoo1567]

Asusal nikil is on fire❤

[@SnigdhaVerma-rc8zl]

nikhil , can we use two for loops for this question?

[@bxp_bass]

That optimization only works in python or other interpreted languages, where sorting is much cheaper than a loop. In golang or c or c++ it's much faster to do loops, so you don't need to spend O(n log n) on sorting

[@muskancreativity7]

Best explanation 💜

[@nikoo28]

Glad that you feel this way :)

[@VaibhavSingh-kh3jr]

Maza aayega ❤

[@quartekstudio8127]

I was stucking this question for 4 days by watching many of videos but I can't find out the best way to answer this question. But you did and explain it really well. I know I'm not that good as problem solving but you are the one who can explain the concept from really hard to a really human can understanding really easy

[@officialdreamplayz]

how many questions u have conquered till now i m on 4th (easy)

[@quartekstudio8127]

@@officialdreamplayz just only 6-7. We are going slow because I think we are missing something or some concept to answer or design to answer the question. I think keep doing it will help us a lot. For me answering in Code war was really easy more than leetcode

[@nikoo28]

all the very best...and glad to see your progress

[@user-fx1kt1ev2b]

Great explanation, but I would add a check for potential issue where an Index error can occur if the first and last strings in the strs array have different lengths. Like this: min_length = min(len(first), len(last)) for i in range(min_length)

[@nikoo28]

Sure, you can do that

[@kshiteeshmani1756]

I tried implementing your code in c++, but I am getting an error on the test case when the input is [" "] in leetcode, how to handle this, because " " in strings would be an empty string.

[@nikoo28]

Check the code in given link in video description. That should help you out.

[@SouravCheck]

2:07, A is also a counted in prefix?

[@denisgordiy5718]

Thank you for great explanation. IMHO more efficiently is not to use StringBulider but just return first.substring(0, index)

[@nikoo28]

The difference will be very minute. :)

[@abhiramsathiraju6276]

Can we optimize it further and make it O(N) ??? Help me if anyone know how to do that!!

[@Atharva_kathiyawadi]

wah bro amazing

[@ashish4k07]

Can O(n) be possible like finding the max lengthed word and least lengthed word and compare them just the doubt

[@nikoo28]

Try writing a pseudo code for it

[@amolgawai010]

Great Explanation, small correction: Space complexity is O(n)

[@nikoo28]

we aren't using any extra space to arrive at the solution

[@CodingJourney-sz3og]

i have a query , why we are comparing rhe first and the last string in the efficient solution after sorting the strings .. after sorting even first two strings can give the solution

[@officialdreamplayz]

clever clue deliver now compare 1st and 2nd 😂

[@rishidangi2978]

first and the last string will have the maximum possible difference, while first and second will have the minimum difference as they're sorted

[@keshavkaushlya8355]

if possible try to show the code for brute force approach also, this helps in understandig the problem in a much better way,btw doing great work,appreciated.

[@nikoo28]

thanks for your feedback and support :)...but usually coding for brute force is not desirable...i only do that in scenarios when you tweak a brute force approach to convert it to an optimal solution.

[@saurabhsaxena8470]

In actual interviews, should we just explain the brute force solution and code only the optimal solution or try to code both?@@nikoo28

[@amitshukla2268]

Hey Bro really thanks, wanna give a suggestion, please use dark color in ppts.

[@nikoo28]

i prefer while, as it gives an experience with whiteboarding as well. You will be doing a lot of whiteboarding in any organization. 😄

[@sahilbait2981]

Please make a video on Repeated String Match question

[@BljtKuntal]

thats great one, but you should also discuss optimised sol also

[@nikoo28]

The optimised solution starts at 07:10

[@devxbasit]

helpful, I just wanted to directly jump to the time complexity timestamp, but could not find it

[@nikoo28]

check the video description please.

[@MaksymKondratiuk]

Thanks for the video. But in the end, it looks a bit confusing. The time complexity of the "brute force" approach should O(n * m) where m is the length of the string and in the case of the "efficient approach" we will have O(n * m * log n) which is slower than the previous one. Is it a case or did I miss something?

[@Ishankulkarni]

You are correct