I've gotten offers before where my answers to at least one of the whiteboard problems looked roughly like "I don't really know how to do this, but I'll see what

I've gotten offers before where my answers to at least one of the whiteboard problems looked roughly like "I don't really know how to do this, but I'll see what progress I can make towards a solution" and either didn't result in a full solution or required pretty extensive help from the interviewer to do so. I've also seen offers made to people who didn't really get a good solution to one of the whiteboard problems posed when I was on the interviewing side but still did well in the rest of the interview and displayed good thinking and problem solving skills even in the question(s) they missed.