i was very very nervious because google was one of my dream companies, and in fact, i solved the same problem at leetcode before, so I memorized the way of solving. When I saw the problem in the real interview, my brain was stopped because I was too nervious and just tried to remember the optimal solution that I memorized previously. and couldn't remember. I think if I didn't solve the problem, probably i would think in a proper way like normally people think and would be able to solve because the problem was not that hard if you are familiar enough with DSA.