Leetcode - Remove Duplicate Letters (Python)

[@janmichaelaustria620]

it took me a while to figure out why answers for the example inputs were the way they were. nice video again Tim!

[@timc3406]

Me too, I thought the question was way too simple at first

[@treyi1794]

shouldn't the condition be while (stack and stack[-1] > s[i] and lookup(stack[-1]) > i ) because its a subsequence and we are removing only duplicate letters?

[@oleksiimartens9779]

Time Complexity of this solution is O(n). We would need to remove 26 elements from the stack at most at each iteration which sets O(1) as the cost of an iteration

[@HD-xn1br]

I like this solution! It seems like we don't actually need to use the seen set though? I removed it entirely and it still passes all test cases. We can just check if s[i] is in the stack.

[@andreawong2935]

The operation "if s[i] in stack" is O(N) where N = len(stack), however, the operation "if s[i] in seen" is O(1), because seen is a set.

[@themagickalmagickman]

I feel silly for looking up the solution now, I shouldve been able to solve this. Need more determination

[@andreawong2935]

Neet!! Thank you for sharing.

[@sharifmansuri607]

Thank you very much for this video. Sir I have a query, why we are not using sorted function. As following s='dcabde' l=sorted(set(s)) print (l)

[@timc3406]

I thought that at first too but we can't because the order of the string matters, we're not allowed to rearrange the letters, we can only remove them as is

[@sajiinsta2026]

how can i have just "a" in the output?i mean remove all two Consecutive letters e.g: input:hhoowaaaareyyoouu expected output:wre how can I do that?

[@chessingh]

this is a different problem, not explained in the video, btw what is the expected output for input:hhoowaaaareyyoouue? Then I can answer this better

[@samarthasthana]

Went the recursive way and regretted it :/

[@timc3406]

LOL that happens to me often

[@vikasviki7490]

Waiting For this , thanks.

[@timc3406]

Thanks for waiting :)

[@sniff4643]

subbed

[@timc3406]

Thanks!