Recursion - Array Questions (Theory + Code + Tips)

In this video, we cover #recursion questions that deal with arrays. This is an important video as it teaches you which technique to use when.
Things like passing arrays in arguments, returning arrays in recursion, creating local objects then sharing values, and more.
Take part in the learning in public initiative! Share your learnings on LinkedIn and Twitter with #DSAwithKunal & don't forget to tag us!
👉 Resources
- Join Replit: join.replit.com/kunal-kushwaha
- Complete Java DSA playlist: • Java + DSA + Interview...
- Code, Assignments, & Notes: github.com/kunal-kushwaha/DSA...
➡️ Connect with me: kunalkushwaha.com
=========================================
Timestamps:
0:00:00 Introduction
0:03:18 Q1 : Sorted Array
0:18:42 Q2 : Linear Search
0:27:09 Q3 : Linear Search (on multiple occurrences)
0:30:50 Q4 : Return an ArrayList
0:49:47 Q5 : Return the list without passing the argument
1:04:19 Q6 : Rotated Binary Search
1:17:52 Outro
#placement #dsa #interviews

[@surajgupta3267]

This man is providing quality content for free...far better than the paid ones ♥️

[@teslatestingwala5019]

He gets Powerfull blessings

[@jayakumar9976]

i can personal vouch for it!!..

[@logeesh2009]

Agreed

[@er.albertaddy2386]

but many important topics mentioned in website are missing, say maps, trees etc. hes also not interested to share.

[@devincodes5218]

No lies... Plus making seemingly hard concepts easy to grasp.

[@rakeshbabu4790]

Increase the frequency of dsa videos Kunal🙏🏻🙏🏻🥺🥺

[@sreejak6776]

Yes! I agree

[@studyafa7159]

Nhi hoga. 🧹🧹

[@demonking7900]

​@@studyafa7159why not

[@_DashingAdi_]

​@@studyafa7159lul

[@roshanchauhan1123]

F = 1 / T but T is regular speed so it will be saame

[@erharshphysics3835]

32:00 😁😁 "You've skipped the course I can't help you. Go watch the video properly" and then you says "ok, I'll repeat it."😂

[@vittalmaheshwari5348]

Hey Kunal it has been a superb journey with you I got a job offer from Microsoft This is all because of your videos and your hardwork Thank a lot Kunal I will support you till my last breath

[@KunalKushwaha]

Glad to hear that!

[@ankitpani6656]

From Which College Are You?

[@omkarjoshi7371]

Offer from these playlist only? Yes no doubt good playlist.

[@mycomputer1429]

Your linked name please

[@mycomputer1429]

Links

[@budgetdapr]

Been going on and off studying CS because I was stuck on recursion. Used to stop studying in a matter of minutes since I couldn't understand anything related to it. Watched 3 videos of your RECURSION PLAYLIST and now recursion is a cakewalk to me. The best 3-4 hours I've ever invested, not even capping

[@KunalKushwaha]

Glad I could help

[@RahulK-lr8ip]

I agree!!

[@panchanansahoo1463]

Thanks kunal for all the videos .But please upload remaining videos after stack and queue as well

[@meetabhashiniparida9417]

@@KunalKushwaha in 1:03:42 why is it returning [3, 4] and not [4, 3]....since its returning from the stack's top, it should first add 4 into the list n then 3 right?

[@ujjwalagnihotri5001]

@@meetabhashiniparida9417 if you haven't still figured out yet, then because call for index =3 will happen first and it will get added in arraylist.

[@vedantyt2451]

Sometimes it's that aura of Kunal which makes us comfortable in getting the hard concepts easily.

[@projecthope2836]

Thanks Kunal, you're really a rare gem, I have understood recursion by just watching your contents

[@albin6126]

your non formal and more friendly way of teaching feel very connected and its like you directly talking to a person

[@subhankarkanrar9494]

If anyone watches the first time, i will say , please see all the videos carefully previously and watch the full video. Don't skip anyone

[@bruvhellnah]

bro did you understand recursion completely from his videos?

[@sharansukesh5542]

Insane teaching man I was able to come up with my own solution in one line for linearsearch return index == arr.length ? false : arr[index] == target || linearSearch(arr, index + 1, target);

[@determinator4491]

You are doing Gods work! So much knowlege with so much clarity for free. Thank you Kunal!

[@ujjwalkumar7267]

Hats off to his calmness, you are such a brilliant tutor, I am new to this channel, going to watch all the videos and learn different concepts..!!!

[@sujithsaikalakonda4863]

Hey, Kunal. Great Explanation. Especially the way you explained 'Return the list without passing the argument' was awesome and clearly understood. Great Work

[@Helly_Patel]

Thanks for teaching us like no one did till now!! One small request, please make lectures on dynamic programming as well!!

[@ashisbhowmik348]

You deserve a Big shoutout ❤️❤️❤️ for providing this type of quality education ..💯💯💯

[@aashashanmugam]

This series is hands down THE best videos on Recursion!! Thanks so much Kunal!!

[@dickharry910]

Best way to learn recursion anywhere. Thank you so much Kunal Sir 🙏

[@riyazahmadkhan9490]

Understanding recursion helping me to understand other data structures in detail and fast too Thank you so much Kunal for providing quality content

[@jamespeterson7824]

Recursion has been explained very nicely ,simple and understandable manner... Good work 🙂

[@sauravagrawal5013]

Simpler code at 1:03:08 is - static ArrayList findAllIndexWithout(int[] arr, int start, int target){ ArrayList arrlist = new ArrayList(); if(start==arr.length){ return arrlist; } // this will contain answer for that function call only. if(arr[start]==target){ arrlist.add(start); } ArrayList ansFromBelowCalls = findAllIndexWithout(arr, start+1, target); // if current arrlist has no value then return the previous ArrayList returns. if (arrlist.size()==0){ return ansFromBelowCalls; } // if current arrlist is not empty then add all the elements from previous arraylist returns to the current arrlist // and return the arrlist. else{ for(Integer i: ansFromBelowCalls){ arrlist.add(i); } return arrlist; } }

[@siddharthdang1521]

concepts explained so well that I would remember for my lifetime

[@AftabAlam-gh1nh]

My code for question at 3:18 public static boolean Check(int arr[]) { int index = 0; return helper(arr, index); } private static boolean helper(int arr[], int index) { if(index==arr.length-1) { return true; } else if(arr[index]>arr[index+1]) { return false; } return helper(arr, index+1); }

[@chinmayatewari7589]

The level of dedication and the quality of content💯.... TONS OF RESPECT AND SUPPORT ❤

[@dark.violin]

Your explanation is really great and I have so much fun watching your videos. Thank you for making a subject like Recursion understandable and entertaining for me.

[@mrrishiraj88]

Good Day! Welcome back! Glad to see n hear you back! 🙏👌👌

[@PriyaSingh-zb5wn]

Thank you for another excellent lecture. It helped me in getting better at recursion .You really know what you are doing.

[@leecha9512]

Awesome explanation and tutorials!!! You made Data Structures, Algorithms, and Recursion dead easy!!!! God bless you beta...

[@jashhinger442]

See you later byeee, at 58:50 that's was so funny🤣🤣🤣 love the way you teach..❤❤🚀🚀

[@ashaysaoji2273]

Excellent explanation for returning a list without passing an argument! Starting Timestamp: 49:47

[@manashbarman273]

Bro please add the tree and graph videos as well.. I am 4 yrs experience at a service based org. But I must say you content is top notch in terms of explanation. I became fan of yours

[@vikaskumarnitrr]

By the time I had subscribed to your channel, I always wait for your next upload just a little request, just increase the speed of uploading videos. love you 3000 Kunal bhaiya

[@entity2.089]

Guess what i checked every dsa course, really couldn't find anything better than this and anyone better than you kunal❤❤❤❤❤❤❤

[@dipeshjadhav1546]

Hats off to the efforts this guy has put in making these videos, Wish we had teachers like this in our collage. I wish you all the luck man and wish all your dreams come true.. Contributing to the better world. Thank you so much man

[@KunalKushwaha]

Thanks a ton

[@aayushojha3088]

Mann you teach so awesome!!!!!!!, i was able to do the subsequence question by passing arraylist in the argument by my own because i had watched you arraylist video and as you keep on telling make the tree so i did that and was able to solve it , so happy mann!!

[@KunalKushwaha]

Glad I could help!

[@shrirambalaji2915]

Thank you so much Kunal, You made this so simple.

[@user-om7vk9gk5k]

yay! just completed the vedio,now I am confident in solving recursion problems

[@shivakumarkonga1532]

Classes are Extremely well......😍😍

[@anishaa3298]

amazing content Kunal, thank you. Waiting for season two :)

[@abdullahalosaimi8506]

Thank you for the amazing work you do. Another solution for question 5 is returning an empty list when the index is greater than or equal to array length instead of creating a new list in every call. def find_all_indcies(target, index): if index >= len(nums): return [] results = find_all_indcies(target, index + 1) if nums[index] == target: results.append(index) return results

[@ridoychandradey8337]

So many things I have learnt so far. This is the best recursion content among all videos in youtube. Thanks a lot KUNAL.

[@_LightingFlash_]

Bro did you have handwritten notes of kunal it's giving me error in github 🥲 plz reply if you have

[@ridoychandradey8337]

@@_LightingFlash_ I have few of these. But not all. When I was taking the notes my handwriting was very messy as well. If you want to know anything then you can tell me and I will give you the fb or linkedin profile link.

[@anirudhchakravarty6373]

Between rotated binary search and recursive binary search which approach do we use in an interview? Love this course btw. Would love to see sliding window, 2 pointer, trees and graph questions

[@imranjamshaid8708]

what a Quality Lectures.I never seen on KZbin

[@meetsoni1938]

The explanation of last question is amazing 🤩🤩💯💯

[@himanshu_1422]

Bhaiya please complete asap these course can't wait for more videos

[@harishs2281]

Yes kunal plz

[@saibrinda8762]

Yes my interviews are on the way 😶this is only hope for coding rounds...thanks for so far🙏

[@prahmodhr3679]

Yes kunal pls finish the bootcamp asap

[@brocklesnar4288]

No kunal bhaiya shouldn't hurry complete it fully

[@samuelmanukonda286]

One of the best courses I have come across so far. You are doing an incredible job. Just a suggestion. People who are having issues understanding the last return statement, try assigning a local variable to it and then return it, so you can see the stack getting cleared after each function call which makes it easier to understand.

[@sameerakhatoon9508]

yep, thanks!!

[@mayank3411]

A really nice work done by you brother...Really a best video of Recursion...

[@pratibhasharma4012]

A big thanks Kunal..for qauality content and with nice explaination

[@maheshgayakwad4227]

bhaiya aapne bola tha ki recurssion me problem aayegi per mujhe to bahut easy lg raha hai ye.... maybe all because u are such a good teacher .. thakyou

[@pradeepella]

Man the dedication ur putting teach all these and ur notes is very much helpfull and ur teaching this for free hatsoff for u, ur best than many other paid courses at present . God ur kunal

[@user-om7vk9gk5k]

bro not many all

[@amruthaa5876]

WOWOWOW I understood the basics well now :D

[@immayurpanchal]

Hey Kunal. Watched your Level 1 Questions video on Recursion and was able to solve one interview questions that I was asked in my interview. Unfortunately, I watched the video after the interview. But no worries. Really the way you're solving questions and explaining the thought process is really really beneficial. I also want to tell you that in the video you sometimes tell that it's too easy and doesn't feel like doing it but still you write the code and explain it. Please do that. It seems too easy for you but it's too difficult for people like me who are not that good at recursion. As you've solved those dumb questions and explained them. Hence, I was able to do some other questions also. This is helping me how to think in recursion. You're doing a fantastic job man! Excited to see your DP, Graph, Tree videos. ❤ I'm happy to tell you that you're not like other KZbinrs and share incomplete knowledge. Kudos to your hard work ☮ 😃

[@user-hm6mv6bx3e]

I can't thankyou enough for this amazing lecture. I understood the whole lecture. If you can make a lecture on DP it will be a big help.

[@chayanbarman337]

now its getting easier for me to solve recursion problem ... thanks ...

[@thanushkrishna2041]

One of the take aways is how to add a result of child recurrisve call to parent recurssive call and carry it forward adding again and again to a parent call !! New concept.. Liked your presentation, thank you !!

[@romanaqureshi7215]

Thanks for the great explanation Kunal..

[@charanteja4619]

Bro simply increasing competition in the Industry!

[@FaizanFurqan034]

Honestly :-> Your teaching way is fantastic and advance level. You are the real example of what's the knowledge we can get from youtube 💯 ❤ Love uhhh bro ❤

[@adilwahla544]

THANK YOU KUNAL for such an amazing content

[@webhelpbyvarghab]

*C++ Code for returning vector without passing answer vector to the recursive function* vectorsolve(int target, vectorarr, int index){ vectorres; if(index==arr.size()) return res; if(target==arr[index])res.push_back(index); vectortemp = solve(target, arr, index+1); if(!res.empty()) temp.push_back(res[0]); return temp; } int main(){ vectorans = solve(4, {3,6,8,9,4,2,4}, 0); for(int x:ans){ cout

[@LowkeyCoder]

best best best especially i was confused at the begining that how the list is geeting returned empty but now its clearer than ever thank you sir 1:02:00.

[@suryaganeshpindiprolu472]

This man is making me fall in love with coding especially recursion

[@shafaq-here]

Debugging makes learning easier . Thanks for the tips .

[@akashnag6459]

No one explained Recursion as easy as you. Thanks a lot. A lot of paid courses doesnt explain Rescursion as you did.

[@KunalKushwaha]

You’re welcome

[@techstar3850]

Great Video. Highly recommended!.

[@sofiyarao815]

guruji MIND IS BLOWN!

[@coder_aditya9567]

Liked the video before watching...coz I know it's amazing ❤️❤️

[@satnamsingh3801]

Your courses are the reason I bought KZbin premium😊

[@sheikhmkrifat7749]

Hats off kunal! take love from Bangladesh!

[@jackofalltradesg]

Love your teaching ❤️

[@rohitpawar3603]

you make my day man, thanks 🙏

[@animeshrose]

Recursion is a cakewalk now! you have my support till the end of times.

[@KunalKushwaha]

Thank You

[@user-vr4ho7zx8c]

Intersting explaining, thank you.

[@poetryiscodingdecoding7965]

One of the finest content of the globe today

[@yaswanthkosuru]

these playlist of recursion deserve million of views

[@haripriyaveluchamy9449]

kunal its my request please make graph videos its really helpful for us...

[@saiakshayyellampalli2599]

Super explaination about array lists in recursion

[@muskanbharti1224]

Great man, great content.. Really need your videos, your tips, kindly start uploading videos... Please kunal.

[@Saeed-Tanjim]

great tutorials man! Thanks a lot

[@Hello1335]

Really loved the video 😍

[@anshvashisht8519]

brilliant concept explained in detail.🤖

[@ankitgiri8394]

Thanks kunal❤😎💯

[@baravi2005]

Can I do a one time payment (instead of monthly subscription)? Brilliant videos...absolutely loving them. I think what's amazing about them is the way the skills are being built up incrementally (like progressive overload for gaining muscle) -this is the key to mastering any skill/subject :)

[@ramanjain7284]

Great explanation especially from 52 minutes onwards concept

[@twi4458]

November 7, 2021: 101,000 subscribers. Thank you Kunal

[@rishabhrawat8197]

you were right now i'm able to solve complex questions in my finger tips

[@KunalKushwaha]

told ya

[@sripraveen2097]

This is GOLD❤

[@beka3304]

I think it's valid also: static List findAllIndex(int[] arr, int target, int index) { List list = new ArrayList(); if (index == arr.length) { return list; } List belowCalls = findAllIndex(arr, target, index + 1); if (arr[index] == target) { belowCalls.add(index); } return belowCalls; } p.s but reversing indeces

[@dinbandhusharma4568]

thanks for this amazing video love this ❣😊

[@sweetyprasad287]

Great work!

[@MuzaUmar]

thanks a lot, no words to describe.

[@user-db9dl7uf2j]

u are the best in teaching broo that u for this course 😘😘

[@khalidalnhdy9776]

Kunal, you are the best ♥

[@faizanshaikh3270]

Do the OOP video ASAP. Because lots of courses do the oop in early part of the course.

[@memestok893]

44:38 code in Python def LiS(arr,target,index,NewList=[]): if index==len(arr)-1: return NewList if arr[index]==target: NewList.append(index) return LiS(arr,target,index=index+1) print(LiS([4,2,3,4,4,4,5],4,0))

[@ayushkumar2418]

Hey @Memestok, did you managed to write 1:03:10 code in python ?

[@ShivamPandey-jc8rh]

never thought these concepts would be so easy to understand bhai agar yhi videos khi hindi me upload maar diye hote to ajj tabahi ho jati cse field me .

[@04.nehalsingh12]

awesome tutorial sir

[@aryanchiyaj7057]

Thanks to provide amazing series till now sir!! please make lectures on dp series as well

[@user-zn1en3hf2w]

can you tell me that while returninig arraylist why the ans is 3,4 instead of 4,3 at timespan arount 1:4:00 plz...

[@gurjargaming863]

Bhaiya you are great aapki wajah se mera recursion itna best hoo gaya he ki me aab koisa bhi question bhot aaram se krr leta huu

[@KunalKushwaha]

You’re welcome

[@Iam_number_one]

THANK YOU SIR !

[@dinosaur37]

hi 1:03:11 here in line 86 the list.addAll(frombelowlist), the list we are talking about is the one that was created first (Suppose L1) in the heap memory, and all the other new lists (L2, L3 , L4 etc.) are just lying there useless. right?