Unique Binary Search Trees II | Similar Problem | Recursion | Memoization | Amazon | Leetcode-95

****************Similar Qns :
Leetcode Link - leetcode.com/problems/all-pos...
KZbin Link - • All Possible Full Bina...
This is the 54th Video on our Dynamic Programming (DP) Playlist.
In this video we will try to solve a very famous DP Problem - Unique Binary Search Trees II (Leetcode-95).
We will solve it using already studied concept (similar qn video link shared above)
Trust me, this will no longer be a Medium Problem.
I will explain the intuition so easily that you will never forget and start seeing this as cakewalk EASYYY.
We will do live coding after explanation and see if we are able to pass all the test cases.
Problem Name : Unique Binary Search Trees II
Company Tags : Amazon
My solutions on Github : github.com/MAZHARMIK/Intervie...
Leetcode Link : leetcode.com/problems/unique-...
My DP Concepts Playlist : • Roadmap for DP | How t...
My Graph Concepts Playlist : • Graph Concepts & Qns -...
My GitHub Repo for interview preparation : github.com/MAZHARMIK/Intervie...
Subscribe to my channel : / @codestorywithmik
Instagram : / codestorywithmik
Facebook : / 100090524295846
Twitter : / cswithmik
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[@AbhishekGupta-if3rb]

Best explanation bhot video dekhi sabne bakwas explanation bataya hai...you are the best ❤.Thank you bro.Ab aaya smj m

[@souravjoshi2293]

Sahi me yaar. Maine 2-3 videos dekhe subah se kyoki aaj late upload kara mik bhaiya ne. Kuch samajh nahi aaya. Abhi mik bhaiya ek video se ek hi Baar me sab clear, I paused the video at 7:32 and using the same concept as the similar Qn, I was able to write the entire code. Salute hai aise teaching skill ko

[@wearevacationuncoverers]

true man

[@ugcwithaddi]

True

[@codestorywithMIK]

It means a lot. Thank you so much ❤️❤️❤️

[@AlishaKhan-ww3io]

Now, I directly come to this channel and wait 😆

[@thevagabond85yt]

much more viewership in lesser time than Larry's YT/@Algorithmist .power of indian market...keep uploading

[@codestorywithMIK]

It means a lot. We Indians are 💪💪💪🇮🇳🪷 Thank you so much ❤️❤️❤️🙏🙏😇😇

[@EB-ot8uu]

India produces best teachers of the world

[@wearevacationuncoverers]

This guys is one fire. He is simply the only guy who can make a Medium/Hard look like a cake walk. I wonder when I will be able to reach at this level

[@souravjoshi2293]

Sabke videos dekha tha aur fir aapke dekhta tha just to compare. Now I only watch your videos. Simplest explanation Hota hai hamesha. Thanks as always

[@sumitbaghel6203]

Phele wali video dekhi thi pr acche se samaj nahi aaya tha pr iss video m samaj aa gaya. Thank you ❤

[@codestorywithMIK]

I am so glad it helped 😇🙏

[@poojabennabhaktula4883]

Kudos to your explanation!!!

[@EB-ot8uu]

insane level. Loved it

[@user-xf3li1lk7l]

bhut pyara khela bhai tumne ...

[@ganeshmula4508]

very good explanation sir,as others said no one didn't given a proper explanation in youtube,thank you sir🙏🙏🙏🙏

[@AlishaKhan-ww3io]

You always make things look so easy. You are the best tutor mik bhaiya

[@tutuimam3381]

Thanks a lot❤❤❤

[@codestorywithMIK]

Hi everyone, Apologies for the delay in upload as you all know that I travel during weekends. 😇 Appreciate your patience . Java Code Below : class Solution { Map memo; public List allPossibleBST(int start, int end) { List res = new ArrayList(); if (start > end) { res.add(null); return res; } if (memo.containsKey(new Pair(start, end))) { return memo.get(new Pair(start, end)); } // Iterate through all values from start to end to construct left and right subtree recursively. for (int i = start; i

[@ugcwithaddi]

Dont apologise sir. You are the best. Please teach us also how to manage time like you 😥

[@recessionriche]

Perfect explanation as always!

[@codestorywithMIK]

Thank you 😇❤️

[@chaitanya812]

Wasn't able to solve 😢 But your video made my day

[@codestorywithMIK]

I am glad my video helped 😇❤️

[@amarnathprajapati2543]

Best Explanation Sir This video is very helpful.🙏🙏

[@codestorywithMIK]

Thank you 😇😇

[@146_shashanks4]

your explanation is very neat and clean bro.

[@codestorywithMIK]

Thank you so much 😇🙏

[@anuppatankar4294]

Great Video 👌🏻

[@Thriftinghai]

Noone teaches like you man. I agree with the Pinned comment. You have the magic of making things simple.

[@anantsingh3079]

thank you 😊

[@ShubhamKumarSingh6224]

bhai kam views wegaira ki wajah se rukna mat bohto achha padha rhe ho aap

[@codestorywithMIK]

Thank you shubham. It means a lot. ❤️❤️😇😇

[@humanity7880]

Amazing explanation sir!!! Much much appreciated please don't stop making these videos one day this channel will hit 1 million soon❤

[@codestorywithMIK]

Means a lot 😇❤️🙏 Hope so it reaches more people ❤️❤️

[@herculean6748]

very well explained!!

[@codestorywithMIK]

Thank you 😇

[@sachinmohanty4577]

🎉🎉✨✨❤️ marking attendance ... MIK can you make of beautiful arrangement 2 question as you said you will try to make it on weekend???

[@codestorywithMIK]

Hey Sachin, apologies. Actually i am travelling this weekend. Will soon try to cover that ❤️❤️❤️😇

[@Prakash_8873]

As usual best explanation. Kabhi kabhi question ka level ka credit bhi App de diya karo😂.Just kidding..... . Literally I feel Todays POTD is little bit tough question .But understand the depth of DP with binary tree concept.

[@codestorywithMIK]

😁 sure Thank you Prakash 😇❤️

[@dayashankarlakhotia4943]

Good explanation please make video on tabulation approach

[@codestorywithMIK]

Sure thing. Will cover in DP concepts soon.

[@top_g755]

Thankyou so much sir❤ may allah give u everything u want

[@codestorywithMIK]

Means a lot 😇❤️

[@top_g755]

@@codestorywithMIK Sir iss question mei aap java ke code mei arraylist function ke andar hi define krr rhe h to recursion jb hoga to baar Barr new arraylist bn jayegi n to purani values kase milegi.... Kya hum jaise mal ko globally banaye h wase list ko nhi bna skte

[@top_g755]

Sir iss question mei aap java ke code mei arraylist function ke andar hi define krr rhe h to recursion jb hoga to baar Barr new arraylist bn jayegi n to purani values kase milegi.... Kya hum jaise mal ko globally banaye h wase list ko nhi bna skte

[@Piyushraj0]

Amazing ❤

[@codestorywithMIK]

Thank you 😇

[@chaitanya812]

what would be the time complexity after memoise ?

[@kishan.17]

Thanks soo much bro.pls make a video on Pointers bro pls ❤

[@codestorywithMIK]

Thank you so much 😇🙏 Can you elaborate what exactly on pointers you want the video ?

[@prashantvishwakarma6100]

I am watching you solutions from last 10 days continuously you explain everything best way i also understand it but i am not able to do it by myself... Without looking at code what i should do ? ...Please Help

[@ss8273]

bhaiya op++

[@codestorywithMIK]

❤️🙏

[@soumyadipmajumdar4306]

using a pair of integers as a key in the unordered_map, and by default, unordered_map does not have a hash function defined for pairs..Need to define our own hash

[@phoddaal7130]

Sir, why it is happening that instead of map, when i used unordered_map. the code stops working. ?? it gave these errors, Line 63: Char 31: error: call to implicitly-deleted default constructor of 'Solution' vector ret = Solution().generateTrees(param_1); return ret; Line 14: Char 54: note: default constructor of 'Solution' is implicitly deleted because field 'mp' has a deleted default constructor unordered_map mp;

[@codestorywithMIK]

C++ doesn’t allow using pair inside unordered map. Hope that helps 😇❤️

[@phoddaal7130]

@@codestorywithMIK ohhh, got it, Thank u sir

[@phoddaal7130]

@@codestorywithMIK Sir can you please tell that, is Competitive Programming Necesaary to crack Big Product Based companies or, DSA and Leetcoding can get me that. Please Tell

[@codestorywithMIK]

Actually competitive programming can help in giving you a boost and confidence of not missing any OA qn. Because OA qns require deep understanding of any Data Structure . But, it’s not mandatory to crack product based companies. Me and many of my mates never did CP. But I believe that today due to excessive competition, sometimes OAs are tough and of CP level but it’s not always the case. So, it’s not mandatory but it’s a good to have if you have enough time.

[@ashutoshpandey1639]

Bhaiya can you explain why we initialize result vector of TreeNode* inside our solve function , because if we make it inside it will just create a new result vector every time when solve function called , if i initialize it globally i gets error

[@codestorywithMIK]

(copied from a comment by @mosereview) - “Every recursive call returns list of roots of different BSTs possible from subtrees. So every recursive call must have different result variable. Keeping it global will keep updating the same result vector in recursive calls because global variables have only one copy.” Above is a good explanation why we keep local result for every recursive call. Hope that helps. 😇❤️

[@ashutoshpandey1639]

@@codestorywithMIK Cleared bhaiya . thanks for reply❤

[@sauravchandra10]

Mujhe laga aaj video nahi ayegi, toh atleast 3 4 videos dekh ke samaj aaya ache se

[@codestorywithMIK]

I hope my video helped. Apologies for delay, as I usually travel during weekends 😇🙏

[@sauravchandra10]

@@codestorywithMIK Aapki videos se kisko nhi samaj ayga 😁

[@codestorywithMIK]

😇😇🙏🙏

[@sauravbiswajit8091]

Thanks a lot

[@codestorywithMIK]

❤️❤️

[@sauravbiswajit8091]

Is it okay to not able to crack this problem although I have solved full binary tree walA PROBLEM , like I feel ki mere se nahin hoga

[@codestorywithMIK]

Yes Saurav, that’s totally fine. Don’t worry. But make sure you understand that the code structure of both problems were similar. So basically this is a pattern and there are similar other qns out there falling under such pattern. I know it’s not possible to remember all pattern. So the best way is to treat every problem as new and start solving it from scratch.

[@sauravbiswajit8091]

@@codestorywithMIK yeah sure thanks sirrr

[@SohelKhan-vt5ql]

what took you so long. Been waiting for ages

[@codestorywithMIK]

Apologies for delay Sohel. Actually i usually travel during weekends. That’s why the delay. I hope my video helped 😇🙏

[@simardeepsinghmudhar7065]

Great Explanation and thanx for telling about the catalan number as well.

[@codestorywithMIK]

Glad it was helpful! 😇🙏

[@Rajdweep]

very hard qs bro

[@codestorywithMIK]

Indeed. For first time its tough. However if you notice the similar Qn in the Description, i had solved it before, so this qn seemed familiar

[@Rajdweep]

@@codestorywithMIK yaa saw that video,getting a pattern,bt have to say the pattern is very rare i have never seen this kinda qs before

[@sourabhsinghbhadouriya9711]

Bhai please also discuss the leetcode contest problems

[@codestorywithMIK]

I will soon start that too ❤️

[@prashantgupta9502]

Please make videos on SQL also only you teach the best way

[@codestorywithMIK]

Thank you Prashant. It’s first time someone has asked me for SQL. I will definitely plan SQL playlist too ❤️😇🙏

[@floatingpoint7629]

thanks for the video. agr algo ko dry kar detay tou aur bhi acha hota 😄

[@codestorywithMIK]

Apologies to have missed that. Actually i travel during weekends, that’s why couldn’t get much time. But for sure I will keep this in mind from next video ❤️❤️❤️

[@floatingpoint7629]

@@codestorywithMIK no problem and please enjoy your weekends. it was a good practice for me. the tree got very big very soon 😂

[@codestorywithMIK]

❤️😇

[@ayushkhandelwal7485]

Bro why does it give error when I use unordered_map for memoization instead of map?

[@codestorywithMIK]

Because C++ doesn’t support pair inside unordered_map. But if you want, you will have to write your own custom hash function for your map. That’s why, it’s better to choose ordered_map

[@ayushkhandelwal7485]

Got it! Thanks sir@@codestorywithMIK

[@amodsings9321]

Title dena bhul gye kya bhaiya?

[@codestorywithMIK]

Just updated Thank you 😇

[@RAHULSHARMA-dl1jc]

bhaiya when i=2 means pointing at 2 ,(leftbst=1,n,2,rightbst=n) then how it supposed to store the elements for(auto lefttree:leftbst){ for(auto righttree: rightbst) { TreeNode* root=new TreeNode(i); root->left=lefttree; root->right=righttree; result.push_back(root); } } please explain this bhaiya

[@wakeuppeggy]

#augustchallengewithmik Love you bhaiya

[@codestorywithMIK]

Let’s keep it going 🔥🔥💪 My full support, love and respect to you guys 😇

[@Yogesh-ei1lg]

Bhaiya aap konsi company mai ho ?

[@amanmathur8602]

plaase make a solution video on leetcode 932

[@codestorywithMIK]

Sure. noted

[@107_faizanalam2]

Sir,I have a question regarding memoization.. Since You have used Map to memoize it.But when we have to use map to memoize it and in which type of question we have to memoize with map instead of simple dp arrays. If you will answer i will be very grateful to you Thanks..

[@ugcwithaddi]

Every recursive call returns list of roots of different BSTs possible from subtrees. So every recursive call must have different result variable. Keeping it global will keep updating the same result vector in recursive calls because global variables have only one copy.

[@codestorywithMIK]

It totally depends on the qn. When you have to store a vector or complex result in dp then choose a map as it will be difficult to maintain that in an array. But if you have to store only a value for a given state, then choose dp array

[@107_faizanalam2]

@@codestorywithMIK Got the point. Thanks a lot sir ☺️

[@utkarshsrivastava5003]

bhai subah se wait kar rahe the yaar

[@codestorywithMIK]

Apologies for delay. Actually i usually travel during weekends. That’s why the delay. I hope my video helped 😇🙏

[@Saryupareen]

can we use unordered map here?

[@codestorywithMIK]

Actually, C++ doesn’t allow using pair inside unordered map. So it won’t work. Hope that helps 😇❤️

[@Saryupareen]

@@codestorywithMIK got it

[@aman3210]

Thanks+4;

[@codestorywithMIK]

😇❤️

[@user-ur9zu1xn5t]

please share notes also

[@adarshdhital007]

Eat, Code,Repeat

[@codeandtalk6]

Solved it on own ❤❤

[@codestorywithMIK]

I am the happiest when i hear this 😇🙏

[@MayankSinghNegi24]

Leetcode 2808 please

[@AbhishekGupta-if3rb]

Description gayab hai bro

[@codestorywithMIK]

Updated 😇

[@jawwadumar2100]

isn't nth Catalan no : (2n)! / ((n + 1)! * n!)

[@codestorywithMIK]

Actually there is an alternative expression for nth catalan number , which you can see here at the wikipedia - en.m.wikipedia.org/wiki/Catalan_number

[@jawwadumar2100]

@@codestorywithMIK yeah okay .. thanks man

[@honey6567]

96. Unique Binary Search Trees From Catalan series class Solution { public: int dp[20]; //catlone number prateek sir write in copy int count(int n ){ if(n==0)return 1; if(dp[n]!=-1)return dp[n]; int ans=0; for(int root=1;root

[@rishabhprasad8638]

what's wrong with this code?? class Solution { List result ; public List generateTrees(int n) { result = new ArrayList(); return solve(1, n); } public List solve(int start, int end){ if(start > end){ result.add(null); return result; } if(start == end){ result.add(new TreeNode(start)); return result; } for(int i=start;i

[@Thriftinghai]

Every recursive call will bring new list of roots of subtree BST. You have used a global result and you are updating same result for every recursive call. Slight modification of your code fixed the issue - class Solution { public List generateTrees(int n) { return solve(1, n); } public List solve(int start, int end){ List result = new ArrayList(); if(start > end){ result.add(null); return result; } if(start == end){ result.add(new TreeNode(start)); return result; } for(int i=start;i