Then you keep interviewing until you get the ones you know. There's luck involved with everything. Luck in the sense of the right time at the right place.
Sorry. Yeah, I probably misread wha you wrote or read some other comment. Anyway, to answer your earlier question, good interviews are a conversation and allow you to demonstrate your knowledge and problem solving abilities. It’s ok to start with a suboptimal solution to a problem and iterate. If you already know the perfect solution to one problem then a good interview will move on to another problem so it’s not that useful.