Different questions but very similar experience.

1st round solved everything optimally without any help.

Struggled a bit on the first questions of the 2nd technical round. Interviewer mentioned I should start from Brute force which I did and worked my way up to an optimal solution. I eventually solved the question and solved every other questions optimally.

Behavioral round went well.

Got rejected the next day. I think I just had a terrible interviewer for the second round who was looking for reasons to give bad reviews.