remove duplicate letters | leetcode 316 | smallest subsequence of distinct characters| leetcode 1081

[@calmyourmind5617]

Very intelligent explaination... Not my cup of tea to understand. anyway thanks.

[@NareshGupta]

hehe - learn practice and apply is the key to success.

[@InsaneRG4172]

whats the space complexity and time complexity?

[@imanhn]

Nice 🙏

[@midasama3124]

Time complexity is O(N) indeed. While loop while traversing string is 26*N is the worst case scenario.

[@protyaybanerjee5051]

Nice explanation

[@NareshGupta]

Keep watching

[@deepankerchaudhary7187]

You earned a subscriber good explanation

[@NareshGupta]

Thanks and welcome

[@muskangupta2545]

Thanks for this wonderful explanation

[@NareshGupta]

Thanks

[@monkeytrollhunter]

I spent an hour and I couldn't get it. so I am here. Thank you

[@NareshGupta]

This problem is little tricky unless you have solved similar problem tuff to come up with solution. Try if not - leetcode.com/problems/remove-k-digits/

[@ManishKumar-eg7ke]

nice one

[@NareshGupta]

Thanks

[@heisenberg1844]

Can you please tell how did you conclude you need a while loop and not a simple if check (just remove the top)?

[@neerajkorde]

you can remove all the prev characters as long as there are more coming ahead(countmap >= 0). Also when 'larger' letters come later, they make a lexicografically smaller word.

[@duongphan219]

So easy to understand. Thanks

[@NareshGupta]

Thanks

[@davidjunghan91]

I participate in leetcode daily quiz. Sometimes I can solve the problem myself. But I usually fail to pass and looking for solutions. Does solutions helps to improve solving skills? When try a new problem, I encounter the same loop..

[@NareshGupta]

Learn and Practice and try to relates problem if you can relate already solved ones. Also, before looking solution try hard and atleast come up with brute force solutions even if TLE in leetcode thats fine. Once you get working solution you can review and try to think if you can improve time. Also, Sometime some problems are tricky which will not easily to come up with solutions so you have to look solution and learn. If you fresh beginner or doing ds-algo after long time - Don't feel disproportionate just keep practice and learn. LeetCode daily challenge problems are randomly selected so any day any topic problem - if you haven't read that topic and solve some standard problem then its tuff so start learning topic-wise parallel.

[@davidjunghan91]

Thank you for replying. I’ll try the standard problems in high priority

[@NareshGupta]

Either follow leetcode explore or interviewbit ds-algo section.

[@rajatgarg2166]

I'm able to understand your approach. Thanks

[@NareshGupta]

You are welcome!

[@nayankhuman1043]

very good explanation sir !!!

[@NareshGupta]

Thanks and welcome

[@VishalSharma-hq5ti]

We could do it without stack also rt?

[@satishshingade8514]

thanks for the solution the problem was really tricky and it was almost looking like dp ..

[@willturner3440]

Dp? Where you find here dp

[@siddharthb2226]

@@willturner3440 lavday, he said it looks like dp. Didnt say it was dp

[@hodex5763]

What do we mean by lexicographical order

[@NareshGupta]

Check the wikipedia you will get good idea - en.wikipedia.org/wiki/Lexicographic_order In general it is sorted order in aphabet. "abc" is lexicographically smaless than "bac".

[@hodex5763]

@@NareshGupta then why not abcd but acbd I searched on Google didn't understood that's why came here

[@NareshGupta]

@@hodex5763 If you taking about the problem example Input: s = "cbacdcbc" Output: "acdb" Here along with lexicographical smallest we have to keep single presence of exiting character and maintain the relative orders. "cbacdcbc" - we have 4 different characters we can remove first c, b as we have more occurrence of c, b later in string with we will get a in starting that will give us start of smallest lexi string.

[@justshanky3012]

How is the time complexity O(n) when we are using a stack? That while loop might also take some time right?

[@ayushagrawal6473]

Each character from string is whether added or removed only once. That means each char is traversed only twice. Which makes it the complexity of O(2*n) ~ O(n).

[@praveenj3112]

We can add unique character in the stack and sort it . Is this work ?

[@NareshGupta]

No, check second example if you sort unique chars abcd will be answer which is not expected.

[@praveenj3112]

@@NareshGupta yes I got it . Thanks

[@PritamKumar-mr5dv]

cool

[@paragroy5359]

Thanks for the video nice explanation....according to me this is a tricky problem tough to solve in the contest if didn't solved such question before

[@NareshGupta]

Thanks. Yes, correct that is the reason keep doing practice.

[@dipteshsil9299]

Hi Naresh, I did not understand how your logic will work for an input like "cba". If I am popping 'c' on encountering 'b' and similarly 'b' on facing 'a', then my stack contains only 'a' after traversing the string.

[@NareshGupta]

You missed the part of lastIndex - this array is used to the purpose of tracking whether if we have same character in string later then only pop from stack if not then don't.

[@willturner3440]

Please make playlist on placement preparation

[@NareshGupta]

Can you help me to share collection of problems

[@willturner3440]

@@NareshGupta yes, share your mail. Then I'll..

[@adarshsharmanit356]

Appreciated Brother !! THanks , Liked ur solution !!

[@NareshGupta]

Always welcome

[@davidjunghan91]

This time it's not easy to understand. But I'll try more

[@NareshGupta]

Keep trying unless you clearly understand

[@tieqi5623]

Watch your video everyday, Really appreciate it. One little suggestion is do better hand writing when you draw the diagram :)

[@NareshGupta]

Noted

[@vedantagarwal22]

You do very good work sir, thankyou !

[@NareshGupta]

Thanks and You are welcome

[@elliotho3015]

really helpful, thank you!

[@Ice-2706]

it was a nice and easy explanation... good job !!

[@NareshGupta]

Thanks, Glad it helped!

[@neerajkorde]

bhai teri handwriting doctor se bhi advanced hai

[@bhargavsai2449]

tu

[@deepakjaiswal1722]

Giving runtime error

[@NareshGupta]

Why? did you found root cause? Or compare with my code in github - github.com/naresh1406/youtube/blob/master/src/main/cp/leetcode/october/Day_11_316_Remove_Duplicate_Letters.java

[@rhythmjayee9707]

very good explanation. Thanks a lot!! keep the good work.

[@NareshGupta]

Thanks. You are welcome!

[@priyanshu.tiwari]

Very poorly explained. Please don't make videos like these.

[@NareshGupta]

What part you didn't understood and not clear?