L12. Print all Permutations of a String/Array | Recursion | Approach - 1

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[arpanbanejee]

it's very rare to find such explanations of recursion! Striver and Aditya Verma both are the best when it comes to recursion! Thanks for making recursion easy :)

[samlinus]

ATTENTION
Are you wondering, why it is ans.add(new ArrayList<>(ds)); instead of ans.add(ds);
If you are using ans.add(ds); ds is passed as shallow copy.. the lists will be added to ans appropriately
BUT as we remove the elements from the list ds since it is a shallow copy it will also be reflected in ans list
Hope this made sense😁

[Manishnapstar]

FOR THOSE, who are not getting "Why we are removing the last element after the recursive call ?". Objects like (Arrays, Maps, Custom class objects etc- all objects) in most programming languages are passed by reference in the function call unlike plain variables (int, char etc), so when you are passing the list/array to the recursive call, any updation(add/remove) on the object will be retained even after the function call finishes. Since for the right/other subtrees (of recursion call) we are not considering the same element. So we need to remove it explicitly.
If you would have passed the new replica/instance of the data structure in every recursive call, then this was not required. Hope this clears the doubt.

[HarshSingh-qqjf]

I came up with the exact 100% logic and code though it took me 3-4 hours but I am so happy that I did solve the problem before looking the approach or the solution all because of the previous problems of the playlist and the beautiful explanation by striver... Though, I could not think of the next approach that is swap, I could only think of the boolean approach

[vitaminprotein]

insted of creating int freq[nums.size()]={0} make itin vector as vector<int>map(nums.size(), 0);

[SAURABHSINGH-xpdm]

Great explanation. U r the lord of Data structure and Algorithm. I sometimes wonder how you understand recursion so beautifully. This is not my cup of tea, if you are not there. Your channel is helping me a lot in understanding advance topics of DSA. I will always be thankful to you

[Code_With_Goat]

faced many difficulties when i am following another source for recursion but after learning from u now I am clear with recursion questions and also able to solve this question myself in 10 minutes thanks striver for the amazing

[SWATISINGH-imrd]

very well understood, Initially i was not able to solve recursion, Dynamic programming problem.But now i am able to do that all, by just following your playlist.

[takeUforward]

Please leave a small comment if you understand by spending your time here, every comment motivates me more :)

[_sayedramishali]

The reccursion tree is really helpful thank u bhaiya🙏

[salmankhader]

Well this can be done in constant space if we just store the character which we are taking in our current permutation in temp variable and change the char by some dummy char or space and recursively call the same function while picking the char ensure that it is not a space. and while doing backtracking we can change the curr char to temp. so that our input string remains same.

[kirtanprajapati]

Thank you so much brother now I'm able to solve recursions questions and also able to understand the behind of approach in recursion and backtracking
Thank you so much You are amazing man.

[mritunjayever]

Thanks, Raj you don't know how much you help college students like me. This explanation was mind-blowing.

[scooby]

Your PlayList for recursion is the best .

[prikshit]

I hope you are doing extremely well bhaiya ❤️❤️

[SatyamKumar-bwvi]

Hare Krishna! Thanks Now I can solve the Problem

[nikhilpandeydigital]

ur explanation had taken me really forward in understanding this problem as well as recursion, HATS OFF to u and ur work ♥🔥🔥🔥

[mohitagarwal]

what if the vector nums contains duplicate elements?...this method would print duplicate permutations as well....eg if the vector contains 1, 1, 2 then the vector<vector<int>> ans would contain {1, 1, 2}, {1, 1, 2}, {1, 2, 1}, {1, 2, 1}, {2, 1, 1} and to remove duplicates without using sets?

[nkgautam]

this is the first ever videos through which i grasp my recursion concept, jiyo striver jiyo

[akshayvishwakarma]

thank you sir, well explained!!, and the map technique with just using an array was genius