C++ Code: github.com/striver79/SDESheet/blob/main/SubsetSumsC%2B%2B Java Code: github.com/striver79/SDESheet/blob/main/SubsetSumsJava Instagram: instagram.com/striver_79/
@parthsalat2 жыл бұрын
Where's the link for the power set?
@aasthachauhan43852 жыл бұрын
can you please make a video on power set as you said?
@aasthachauhan43852 жыл бұрын
kzbin.info/www/bejne/mGikipWmgpqMqKc the link for powerset
@takeUforward2 жыл бұрын
@@aasthachauhan4385 it is there
@parthsalat2 жыл бұрын
@@aasthachauhan4385 Power set is very easy...spend some time on it and you yourself can develop an algorithm for it
@lavanya_m013 жыл бұрын
You have a lot of patience to trace out the whole recursion tree.. thanks a lot for this :)
@debjitdutta172 жыл бұрын
what else do you expect from a 6star coder,these nothing for him xD
@rohanmishra2936 Жыл бұрын
humility is very rare these days though@@debjitdutta17
@anushakulkarni84902 жыл бұрын
The first recursion sum I solved on my own and got accepted in the first go....thank u so much !!
@nahidfaraji5069 Жыл бұрын
Same goes with me. Hehhehe
@nithish52963 ай бұрын
Same Broooooooooo !
@MohanRam-mq2pk2 ай бұрын
same!!
@kumarsaurabhraj25383 жыл бұрын
The time complexity of the recursive solution is also 2^N x N. We know that we will get 2^N subset sums and at last we sort the array so 2^N + (2^N)log(2^N) ~= 2^N x N
@srikanthmathala940 Жыл бұрын
For simple variables (non-container types like int, float, etc.)(here it is sum), we don't need to adjust them explicitly after including them in a recursive call. The reason is each recursive call creates its own local variables, and any modifications we make within a recursive call are isolated and do not affect other recursive calls.
@niyammuliya57872 жыл бұрын
If we sort the array before passing in function func, then no need to sort sumSubset array by doing this, We have also reduced the time complexity from O ( 2^n + (2^n) log(2^n)) to O (2^n + n Log(n)).
@venkateshn98842 жыл бұрын
Yeah..but for that we we need to call right subtree before calling left subtree.
@rakshankotian27372 жыл бұрын
@@venkateshn9884 we need to sort in decreasing order in that case rit?
@venkateshn98842 жыл бұрын
@@rakshankotian2737 Exactly 💯
@user-le6ts6ci7h2 жыл бұрын
You can't always do that , there could be chances , for certain test cases where the sorting order might go out of order Example [6,4,3,2]
@amitranjan69982 жыл бұрын
@@user-le6ts6ci7h Nooo ....it will also work ,if you sort at starting ,we can achieve using O (2^n + n Log(n)),no issue on this
@amanbhadani88402 жыл бұрын
The way you makes us understand each and every concept is just incredible bhaiya.For those finding it tough or not confident enough in recursion,i would suggest to solve more questions on trees.
@growcodeyt72562 жыл бұрын
The first recursive approach which I understood clearly.. Thank you so much sir.
@imranimmu4714 Жыл бұрын
Couldn't Thank you enough Raj bhaiyya, I am currently going through Recursion playlist of yours, and I could absolutley say ,no one could have taught us better than this. Thank u soo much for your work.
@VishalGupta-xw2rp2 жыл бұрын
I was able to grasp this as it's a kind of Subsequence but we are only concerned with its Sum..... To think i was able to think of a logic myself.... Wowww all thanx to you 🙏♥️🤩🔥
@shivamshrey472 жыл бұрын
If you just reverse the order of recursive calls (don't pick first and pick second), you would automatically get the resultant subset sum array in sorted form. This way one can avoid the final sorting of the result.
@pavanpatel6877 Жыл бұрын
Woahh...That's a good observation though. Thanks shivam!
@26.aniketmatkar20 Жыл бұрын
No it will not work, it will just reverse the answer vector. One element i.e 4 will remain unsorted
@subham8746 Жыл бұрын
No it'll only reverse the output, it won't be sorted.
@Siscerto Жыл бұрын
@@26.aniketmatkar20 bruh,,, it literally passed,,, and its sorted... idk how its getting sorted tho.. gotta draw recursive tree... however they never asked for sorted output tho ArrayList subsetSums(ArrayList arr, int N){ // code here ArrayList sol = new ArrayList(); setsum(sol,arr,N,0,0); return sol; } void setsum(ArrayList sol, ArrayList arr, int N, int i, int sum){ if(i==N){ sol.add(sum); return; } // 1.skip ele and proceed setsum(sol,arr,N,i+1,sum); // 2.pick ele, add sum and proceed setsum(sol,arr,N,i+1,sum+arr.get(i)); }
@Siscerto Жыл бұрын
The thing is we dont need to SORT, they're sorting it in the DRIVER code
@Rajesh-op8zx2 жыл бұрын
Actually we dont need to sort because if you first call for not pick then pick we get subset sum in ascending order thus T.C= O(2^N) . Code that is submited without sorting : void fun(int index, int sum , vector &arr,int N,vector &ans) { if(index==N) { ans.push_back(sum); return; } fun(index+1,sum,arr,N,ans); fun(index+1,sum+arr[index],arr,N,ans); } vector subsetSums(vector arr, int N) { vector ans; fun(0,0,arr,N,ans); return ans; }
@tanyagupta11762 жыл бұрын
Hey , can you explain why we are not subtracting arr[i] from sum when backtracking in case of not take.
@tanyagupta11762 жыл бұрын
@22.37
@stepup70522 жыл бұрын
@@tanyagupta1176 beacuse we dont add it we just skip that index in parameter
@mriduljain1981 Жыл бұрын
we can reduce the time for sorting by modifying the code as below - void solve(vector arr,int i,vector &ans,int sum){ if(i == arr.size()){ ans.push_back(sum); return; } solve(arr,i+1,ans,sum); sum = sum + arr[i]; solve(arr,i+1,ans,sum); } vector subsetSums(vector arr, int N) { vector ans; solve(arr,0,ans,0); return ans; }
@tanujabetha54006 ай бұрын
Just a doubt in the code: When you are doing sum + arr[i], that means you are picking that element right. When you do to not pick recursion, dont you have to do sum = sum - arr[i] and then call recursion.
@princerajput67092 жыл бұрын
I have made this question from myself using both iterative and recursive approach thanks striver from bottom of my heart ❤
@anishkarthik4309 Жыл бұрын
We just need to sort the initial array(n logn) , and do not pick and then pick. So we end up getting an array of sums in sorting order(2^n for generating) T.c = O(n logn + 2^n) = O(2^n) S.c = O(2^n)
@idiot3641 Жыл бұрын
it wont't work
@yashlad8752 жыл бұрын
@take U forward Thanks for the amazing recursion and dynamic programming series, For this question I think we can have TC = 2^N by sorting the given array first and deciding to not pick before picking. That way the resultant array will be in sorted order!
@mridulshroff8242 жыл бұрын
Can you explain how not picking before picking reduces TC? I couldn't understand.
@shiyadh44712 жыл бұрын
@@mridulshroff824 Because we need to reach to the lower sums before reaching to higher sum values.For example, take [ 2, 5, 1] as the arr.We sort it to [ 1, 2, 5] why? bcz, we will go and find all possible subsets starting with 1 ,then with 2 then only 5 - thus they will be in ascending order.Now, lets say you have slected [1,2] and the recursion call is suppose to pick/not pick the element 5 , by not picking it, my sum is 1+2=3 but by picking its 1+2+5=8 . so, which call i should make to get the least sum first(ascending order) ? Its the not pick case right ...
@shashankdixit922 жыл бұрын
I think if we select not picking first, then in the Array (1,2,3) 3 would be picked up first...
@yashlad8752 жыл бұрын
@@mridulshroff824 Because then we don't need to sort the output array in the end.
@yuvrajluhach56652 жыл бұрын
Moving to L11 , this was an easy one 👍
@mountINEER11 ай бұрын
solved this under a minute, really quality content , best way to give back your learnings, true guru !!! . Eagerly waiting to meet you one day and I surely will ..
@s.g.prajapati35973 жыл бұрын
First Viewer, just wanted to say, You're doing amazing job! Keep up the good work!
@ganapatibiswas58582 жыл бұрын
We can sort the input array and then do recursion such a way that we take smallest elements first. This will generate subset sum smallest to largest and we don't need to sort the final array at the end.
@your_name962 жыл бұрын
umm, so you are adding code/logic complexity with no improvement in time complexity ?
@ganapatibiswas58582 жыл бұрын
@@your_name96 no we don't need to sort the final array which has the size of 2^n. We sort the input array which has size n. So time complexity will be less.
@your_name962 жыл бұрын
@@ganapatibiswas5858 oh yes,will try to implement this one
@codediary25682 жыл бұрын
he is a legend for the first time I have solved a recursion question myself
@shreyxnsh.144 ай бұрын
Thnaks striver, did all that by myself by just seeing half the approach.
@yogeshvaishnav64643 жыл бұрын
You said TC of recursive solution is 2^N + 2^N log (2^N), isn't it equal to 2^N + N*2^n(log 2) = N*2^N + 2^N = O(N * 2^N) same as iterative one?
@deanwinchester86913 жыл бұрын
yes you're right.
@democratcobra3 жыл бұрын
Thanks a lot for adding the visualization of the RECURSIVE CALL, it really helps in getting the proper understanding. Thanks a lot for your effort and hardwrork. Really Helpful.After watching this i am going to be member of your chanel.Really well explained.
@shashwatpandey82432 жыл бұрын
instead of sorting the array with subsets sum, we can just sort the array which contains n elements. and then we have to first call the function in which we do not include current element in the sum. this will result in sorted result only. and also sorting time would be reduced
@saddy44202 жыл бұрын
Same this will reduce the TC from 2n log 2n to n log n
@namansharma73282 жыл бұрын
📢🔥🔥What is the space complexity?????? Is it O(N) cuz at max there would be N revursive call waiting in the stack. (there are n+1 levels in the stack space tree). Plz clarify
@ankittjindal2 жыл бұрын
ye qsn sbse easy tha phle k 2-3 lectures me qsns ko 2-3 bar rewind krke dekhna pdh rha tha lekin isme niii thnx😃
@funnythings86033 ай бұрын
why sum is not minus when we came back and go to not pick option?
@Bharat_Rider Жыл бұрын
Understood bro i just understood the method without pseudo code and wrote program myself. Great explanation
@utkarshsarin94432 жыл бұрын
Thank you so much Bhaiya...I am starting to get a better idea of recursive calls know and I am say this with a 100% certainity that your videos have a major role in all this ❤
@paulbarsha1740 Жыл бұрын
understood sir, but why we are sorting it again in the main function? i saw this in the documentation of this problem int main() { vector < int > arr{3,1,2}; Solution ob; vector < int > ans = ob.subsetSums(arr, arr.size()); sort(ans.begin(), ans.end()); cout
@atharvakulkarni20243 жыл бұрын
BHAIYYA PLEASE EK REQUEST HAI EK VIDEO ISPE BHI BANAO DEPTH ME KI HUM POP BACK KAB KARTE HAI BACKTRACK KE TIME USME BOHOT CONFUSION HO RAHA HAI
@akshaykenjale26422 жыл бұрын
So basically how we can differentiate between subsequence and subset, subsequence can be like which follows order of array, but then too need some more points
@tasneemayham974 Жыл бұрын
STRIVERR!! I watched the first couple of minutes of your video and then was able to code the solution alone!!! Thank you for the amazing content!!!!!!
@Suryansh_Goel.8 күн бұрын
sorting the given array in decreasing order and doing not pick before pick will reduce the time complexity a little as the final answer will not need sorting
@AmanKumar-dl8os Жыл бұрын
we can remove the time complexity of sorting the solution by making the right sub-tree to the left and the left sub-tree to the right. Please try it once, this means swapping the recursive function calls.
@chetanguduru2 жыл бұрын
I have done using this method. Does this have any down side? There is no requirement of sorting here vector subsetSums(vector arr, int N) { if(N == 0) { vector ans; ans.push_back(0); return ans; } vector output = subsetSums(arr,N-1); int size = output.size(); for(int i=0;i
@Anjaliojha-o2lСағат бұрын
agar hmlog given array ko phle hi sort kr de decreasing order me aur not pick wala function call pick wale function call k phle rkh de, to hme apne ans ko alag se sort krne ki jarurat nahi pdegi, and aise hm 2^n*log(2^n) T.C ko n*logn se optimise kr skte h.
@artifice_abhi2 жыл бұрын
Bhaiya mtlb kaise btaun apne to kamal kardia ye question mne khud try kia aur first attempt m kardia Apse padhkar maza agya.
@Bharat_Rider Жыл бұрын
If someone does this tracing for merge sort till the end his confidence increases a lot in recursion
@alexquistain45092 жыл бұрын
Best explanation i have found here in this video thanks a lot for ur hard work nd keep doing
@daksh80552 жыл бұрын
I have a doubt that when do we make the helper function return something and when do we not return anything, would it be possible if in this solution the 'func' functions return the final arraylist?
@shashankpandey6230 Жыл бұрын
instead of storing it in arraylist we can use treeset to reduce the extra overhead of sorting the list
@vishious14 Жыл бұрын
TreeSet would still take logN time to insert each sum. So for n subsets sum it'll take n*logn time, which is same as sorting the final container.
@roushanraj85303 жыл бұрын
thank you bhaiya, for your awesome informative videos of most important DSA question, aap jldi thik ho jao ......
@sonalisinha325 Жыл бұрын
why have you not used sum = sum-arr[index] before 19 statement
@lakshsinghania Жыл бұрын
thnks bhaiya i was able to do combination sum 3 on my own only because of u
@aravindben6254 Жыл бұрын
The below code avoids sorting and has O(2^n) time complexity instead of O(2^n)+O(2^n log(2^n)) void comb(vector &sums, vector &arr, int i, int n, int sum){ if(i>=n){ sums.emplace_back(sum); return; } comb(sums,arr,i+1,n,sum); comb(sums,arr,i+1,n,sum+arr[i]); } vector subsetSums(vector arr, int N) { // Write Your Code here vector sums; comb(sums,arr,0,N,0); return sums; }
@ompandey84702 жыл бұрын
congratulations bhaiya apka google me hogya na!, Main bhi aa rha hu jldi hi milte hai
@HarshitMaurya2 жыл бұрын
looking at these combination problam at saying abhi to ye sb bhaiya ye padhaya subsequences me tha and then i tried myself and got ac , best feeling ever
@VY-zt3ph Жыл бұрын
The space complexity here will be of O(N) because that will be the depth of the recurs ion tree.
@ankursingh8296 Жыл бұрын
Sort array in reverse order and do not take first and next call for take this way we get sum in inc order automatically..I am assuming all elts to be distinct..tc 2^n and SC is 2^n
@abhisheksa663511 ай бұрын
Because of the earlier videos and ruminating in my sleep, I could solve this, honestly I did one mistake that is keeping a vector storing the subset, should have saved a sum variable.
@mohitkumarbansal34863 жыл бұрын
I really afraid of this questions but when I see your video some magic happen
@gepliprl85582 жыл бұрын
Thank you for using real english. I subscribe your soul 👍
@saketjaiswalSJ Жыл бұрын
//sum of subsets in sorted order //t.c is for every index i have two choice pick and not pick for example i have 3 indxes the i will //have total 6 choices p/np for each indexs hence for n indexes i will have 2^n choicess //also there is extra 2^n*log(2^n) t.c for sorting the ans array hence total t.c is (2^n * 2^n *log(2^n)) class Solution { public: void solve(vector &a, int index,int s,int N,vector &ans) { if(index==N) { ans.push_back(s); return; } //picking element from the index solve(a,index+1,s+a[index],N,ans); // s=s-a[index];aisa kuch nhi hoga s datastructure nhi hai //s ek simple variable hai samjha kuch nhi krna hai //decreasing the sum //simple backtrack //pick notpick ka function easily call ho jayega samjha be solve(a,index+1,s,N,ans); } public: vector subsetSums(vector a, int N) { vectorans; int index=0; int s=0; solve(a,index,s,N,ans); sort(ans.begin(),ans.end() ); return ans; } };
@akshatjain34842 ай бұрын
one of the best explanation!!!!!!!!
@fivexx4692 жыл бұрын
do we even need to sort the array ,as it is not asked in the question?
@ranasauravsingh2 жыл бұрын
UNDERSTOOD... !!! Thanks striver for the video... :)
@madhurgupta38492 жыл бұрын
I think It can be done in single recursive call. vector subset(vector &num,int i) { // Write your code here. vector ans; if(i==num.size()){ ans.push_back(0); return ans; } ans = subset(num,i+1); int size=ans.size(); for(int j=0;j
@ishanmoykhede94846 ай бұрын
solved in 8 min just by reading problem statement ❤🔥❤🔥❤🔥
@ankityadav69143 жыл бұрын
I do think so that the time complexity of this approach would be O(2^nlog(2^n)) = O(n* 2^n). Please have a look at my code below, it is accepted on gfg and I think it is having time complexity O(2^n) only, please correct me I am wrong. The idea is still similar to either pick an element or not pick the element but we are only pushing sum+arr[n-1] value into the vector. Also, the recursive function will not consider of the case when no element is picked hence we have to push_back(0) into the vector at the very beginning. void subSum(vector &arr, int n, int sum, vector &s) { if(n == 0) { return; } s.push_back(sum+arr[n-1]); subSum(arr, n-1, sum, s); subSum(arr, n-1, sum+arr[n-1], s); } vector subsetSums(vector arr, int N) { vector s; s.push_back(0); subSum(arr, N, 0, s); return s; }
@armed37192 жыл бұрын
why r we not removing here like we did in other problems
@pirangitharun87363 жыл бұрын
Can be done in 3 ways [Bit manipulation, DP, Recursion]
@takeUforward3 жыл бұрын
Dp wont be possible as you need to print sums so you need to go to the depth always.
@pirangitharun87363 жыл бұрын
@@takeUforward Thanks for the mention bro
@siddhartharathour1802 Жыл бұрын
if we call the function that does not include first element in current sum and then call second function. then we will get subset sum in sorted order than there is not need to sort. public void ss(ArrayList arr, int n,int sum,ArrayList sub){ // code here if(n==arr.size()) { sub.add(sum); return ; } ss(arr,n+1,sum,sub); ss(arr,n+1,sum+arr.get(n),sub); }
@venkythesmart4402 жыл бұрын
you are doing amazing job ! keep up good work!
@chiragarora8703 жыл бұрын
Sorting isn't required, driver code is automatically sorting our array
@aftabansari38452 жыл бұрын
Submitted successfully w/o sorting the result array.
@vyankateshkulkarni4374 Жыл бұрын
Thanks striver. you made understanding so easy. thanks brother
@a.yashwanth2 жыл бұрын
Without sorting also all testcases passed for me in GFG.
@naveenkumars18563 жыл бұрын
i have an good resume sir ., i find no ways to join Directi for SDE
@thexhist3609 Жыл бұрын
whats the difference between recursion of subsequence and subset , isn't both of them same
@Sarkar.editsz2 жыл бұрын
Thanks a lot , i did this question all by myself becoz of your videos and your guidance , thanks a lot
@dewanandkumar85893 ай бұрын
Understood
@prabhakaran55423 ай бұрын
Understood ❤
@amityadav-km5rx10 ай бұрын
Very Nice Lecture
@leo-x1d1f2 жыл бұрын
best think of striver bhaiyya videos is promotion tell (time) so we can skip promotion easily every youtuber have to do this
@aysams2 Жыл бұрын
In the recursive fxn, why is the condition if( ind == N) and why not if( ind == N-1) as we're using 0 base indexing ???
@Lullurluli9 ай бұрын
It is zero based indexing but on function call we are incrementing ind + 1 so it will return as n == ind
@jha.brajesh6 ай бұрын
2:20 GFG edited their expected space complexity
@anirudhsoni60013 жыл бұрын
Thanks for the video. What if question is twisted a little bit and we have to find the smallest subset sum value which cannot be formed? Ty!
@thegreekgoat982 жыл бұрын
That's a good question
@TheElevatedGuy2 жыл бұрын
can we store ans in a multiset and covert to vector and return. By the way thank you very mush for this playlist.
@apoorvgupta1211 Жыл бұрын
Hey Striver, Big fan and thank you for the amazing series, but in this question, we are asked about subsets and what you have explained is the solution for subsequences. In your video on subsequences, you had explained the difference between subsets and subsequences - "Subsequences can be contiguous as well as non-contiguous but subsets are always contiguous". This point can also be observed if we go to the problem link and see the examples mentioned.
@kaichang81866 күн бұрын
understood, thanks for the perfect explanation
@GeneralistDev Жыл бұрын
void dfs(vector &nums,vector &ans,int idx, int sum){ if(idx>=nums.size()){ ans.emplace_back(sum); return; } // take dfs(nums,ans,idx+1,sum+nums[idx]); // not take dfs(nums,ans,idx+1,sum); } public: vector subsetSums(vector arr, int N) { vector ans; dfs(arr,ans,0,0); return ans; }
@parthsalat2 жыл бұрын
Where's the link for the power set?
@anubhabpaul7160 Жыл бұрын
Can anybody tell.. why we r not doing sum-arr[i] when we r returning... so the previous sum dont add... as we do in other subset problem
@CodeRocks-z6g4 ай бұрын
we are passing sum+arr[i] directly so when recursion return and goes to not take f(ind,sum) sum is passed not sum+arr[ind]
@chennurugurusankar2955 Жыл бұрын
We should not consider input and output in space complexity right then space complexity will be O(N)
@roliagrawal3124 Жыл бұрын
Just one confirmation i need incase of list we remove last element and incase of variable we just return it. It happens because of pass by value and pass by reference?
@neyovyas39923 жыл бұрын
Please try to upload video daily and love your videos and explanation too much
@shivamsrivastava101711 ай бұрын
Are we allowed to return same sum multiple times in the array if sum of different subsets is the same
@rpriyanka285 ай бұрын
he is the definition of handsome with brains!!
@ankushladani496 Жыл бұрын
I think code is written wrong Because we have to backtrack also So sum should be subtracted before another recursive call
@udiiiiiit5020 Жыл бұрын
We pass sum+arr[i] to next function call when picking the current element and do not change the value of sum itself, so when going for not picking recursive call we just pass sum.
@atulpardhi94992 жыл бұрын
bhaiya sheet ke only 180 question ki practice se interview crack ho skta hai kya. my 3rd year is going to end and in have not prepared yet? plz help bhaiya.
@akshayrathod76792 жыл бұрын
Dont worry u have time
@RoushanKumar-dp2qq2 жыл бұрын
I guess Time Complexity can be reduced significantly!! Instead of sorting the result array of size of size 2^n we can sort the input array of size of size n. And while picking instead of pick, FIRST perform NOT pick THEN pick class Solution{ ArrayList subsetSums(ArrayList arr, int N){ Collections.sort(arr); ArrayList result = new ArrayList(); subsetSums(0, 0, arr, result); return result; } void subsetSums(int i, int currSum, ArrayList arr, ArrayList result) { if(i == arr.size()) { result.add(currSum); return; } //not pick ith element for sum subsetSums(i+1, currSum, arr, result); //pick ith element for sum subsetSums(i+1, currSum+arr.get(i), arr, result); } }
@nileshchandra64352 жыл бұрын
Not really. for [1,2,3]. the subset sum for [3] will occur before [1]. So, the final answer would still be unsorted.
@RoushanKumar-dp2qq2 жыл бұрын
@@nileshchandra6435 can u please elaborate your point, as the code above passes all the test cases on GFG including [1,2,3] (as first I am performing NOT pick then PICK)
@shyamaprasadmohanty621511 ай бұрын
Note: You don't need to explicitly backtrack here because the recursive stack itself takes care of the variable sum's state!
@ritikshandilya70755 ай бұрын
Thankyou so much for great content Striver
@vikramjha4 Жыл бұрын
Can't thank you enough for these videos!
@kirthe1116 Жыл бұрын
When to use pick/nopick method and when to use strategy mentioned in previous vide is confusing. Can someone clarify
@amitrawat8879 Жыл бұрын
you can use different methods according to the constraints given in the question. like if the constraint for time complexity is 2^n then you can use recurrsion, other can use other optimal solutions.
@NamasteJi-c1v Жыл бұрын
May be I am not able to understand the logic properly but to the extent that I understand I had one doubt when we don't pick any index then our sum is 0, and when we move to left of that than also our sum will be 0 so what I am trying to say is that we should be having duplicate values, can some one help me and let me know, if I am missing something
@mayankjaiswal14922 жыл бұрын
man, this is a banger, thank you so much for this
@parthsalat2 жыл бұрын
C++ code at 23:50 Complexity analysis at 20:05
@nirmalkishore9226 Жыл бұрын
what is the difference between subsequence and subsets?