1. The candidate has a solid understanding of the template system in C++. Chances are pretty high that he has a similarly high understanding of other parts (which would come out with further discussions during the interview).
2. The candidate is a creative thinker, which is hugely important in a profession where you tend to get blocked by faulty or incomplete tools, or tools not designed for what you want to do.
3. The candidate is highly intelligent and inquisitive, which means he'll likely have more success in exploratory tasks, and he'll likely have a greater breadth and possibly depth of exposure in general.
Comments
What I would take away from this mad display:
1. The candidate has a solid understanding of the template system in C++. Chances are pretty high that he has a similarly high understanding of other parts (which would come out with further discussions during the interview).
2. The candidate is a creative thinker, which is hugely important in a profession where you tend to get blocked by faulty or incomplete tools, or tools not designed for what you want to do.
3. The candidate is highly intelligent and inquisitive, which means he'll likely have more success in exploratory tasks, and he'll likely have a greater breadth and possibly depth of exposure in general.
4. The candidate can program (of course).
5. Candidate likely has a pretty good sense of humour.