I got explicitly failed from a first round interview because I took too long to solve a graph traversal problem. I reasoned my way through and got to the optima

I got explicitly failed from a first round interview because I took too long to solve a graph traversal problem. I reasoned my way through and got to the optimal solution, the interviewer confirmed that it was the optimal solution, then said I "should have recognized a variant of Dijkstra's algorithm" and that I had failed for not knowing it in advance. Personally, I think developing it from scratch shows more promise than memory, but a lot of employers are looking for the inverse right now, IME. edit: and this was not a FAANG, this was a startup with a single digit number of employees!