Lecture 66: Construct a Binary Tree from InOrder/PreOrder/PostOrder Traversal

In this Video, we are going to solve TREE Important Interview Questions.

There is a lot to learn, Keep in mind “ Mnn bhot karega k chor yrr apne se nahi hoga ya maza nahi aara, Just ask 1 question “ Why I started ? “

Questions Links:



Do provide you feedback in the comments, we are going to make it best collectively.

Connect with me here:

Telegram Group Link: Love Babbar CODE HELP

Intro Sequence: We have bought all the required Licenses of the Audio, Video & Animation used.

Timestamps:

00:00 - Question 1
02:53 - Approach
11:05 - Code
22:38 - Question 2
23:40 - Approach
27:20 - Code

#DSABusted #LoveBabbar

[anuragpandey]

30:15 You clearly have a strong understanding about where the students could get stuck. Much love

[topshorts]

The code mentioned in the video doesn't passes updated testcases -->
So here is the updated code -->
class Solution{
private:
int Findposition(int in[], int inorderStart, int inorderEnd, int element, int n){
for(int i = inorderStart ; i<=inorderEnd ;i++){
if(in[i]==element){
return i ;
}
}
return -1 ;
}
Node* solve(int in[], int pre[], int &index, int inorderStart, int inorderEnd, int n){
if(index>=n || inorderStart>inorderEnd){
return NULL ;
}

int element = pre[index++] ; // At every interation index is increasing
Node* root = new Node(element);
int position = Findposition(in, inorderStart, inorderEnd, element, n);

root->left = solve(in, pre, index , inorderStart, position-1, n);
root->right = solve(in, pre, index, position+1, inorderEnd, n);

return root ;

}
public:

Node* buildTree(int in[], int pre[], int n)
{
// Code here
int preorderindex = 0 ; //Pre order is NLR so First element is root .

Node* ans = solve(in, pre, preorderindex, 0 , n-1, n );
return ans ;
}

[anmol]

Question 1 Test case 54 fails after addition of new test case
Solution:
Can't use maps. Use findPosition function and pass inorderStart and inorderEnd as arguments and not n(size). This happens because elements might be repeated.

[govindsuryavanshi]

First I have completed all DSA series and now conclude this is Greatest ever DSA series to exist on youtube or paid courses. Your contribution will be remembered. You're God of DSA for us🙇‍♂ Thanks you.

[simplesolutions]

Best course!
Best teacher!
*Best time to learn!* 🔥

[aayushiagarwal]

Thank you sir :), for making tree simple and understandable .
I would like to highlight one point :
Mapping solution will give wrong answer in case of duplicated in such case, we can optimize findpos() function by checking from inStart to inEND ..
int findpos(int in[], int x, int n, int s, int e)
{
for(int i=s;i<=e;i++)
{
if(in[i]==x)
return i;
}
}😇

[prerakagarwal]

You are doing literally a very good job. I got to understand many concepts easily after watching your videos. Trees are very well explained. Many Thanks.

[kritarthtripathi]

Best DSA course and consistency ++...Thank u so much for your effort❤

[prashantbirajdar]

wah bhaiyaa ..another an exciting session i understood every thing from this session thanks bhiyaa for providing free of cost DSA course...loves the most...content and your teaching technique is so optimistic...thanks again

[rampratapmishra]

Wahh... Bhaiya mann gya aapko.. Kya consistency ha aapkee.. Ham ek video dekh nhi paarahe.. Aur aapke... New video... Aa rahe.. Ha bhaut saahi bhaiya..
Bass.. Aise hee consistentsy ham bhi continue kar paaye... Great bhaiya really great fan of 🤗🤗

[prabhatm]

Great Efforts Sir....I think who wants to learn tree this is the platform

[ayushkiledar]

Awesome!! The best DSA anyone can teach!!

[ankitgaur]

Bhai Lecture 66 onwards code ko github mai push kyo nhi kar rhe ho? Repo se code samajna easy rehta hai. during videos hum code samaj sakte and then after completion of video hum code repo se notedown kar sakte hai. so pls push code from lecture 66 onwards in github repo.

[anuragmalviya]

Bhaiya ki knowledge, video uploading me consistency, or way of explanation top notch hai!🔥🔥🔥

[chandrabhanbahetwar]

It is the best dsa course in the you tube bhaiya carry on we all are with you 🌹🌹

[scocvora]

A Very WELL EXPLANATION wala Video and Insane amount of Effort of Love Bhaiya is clearly vivble and For that Again and Again Explanation Thank you bhaiya

[nishankdas]

Amazing observation bro on the inorder to postorder question. I have never thought it that way.

[adityacreator]

Ek ek chize achche se explain kiya apne great bhaiya 💯

[vinayakgarg]

Here we can also use unordered map (T.C - O(1)) as we don't need data to be sorted, so the overall t.c will be O(n)

[pavanmutalikdesai]

Best explanation!!! You make solutions look so simple.