4 ms·

I feel like there is unlikely to be a solution which doesn't involve (1) brute force, or (2) higher-level theory (i.e. eigenvectors and eigenvalues). Prove me

I feel like there is unlikely to be a solution which doesn't involve (1) brute force, or (2) higher-level theory (i.e. eigenvectors and eigenvalues). Prove me wrong, and I will be tripping over myself to upvote you ;)

gruseom 15y ago
Certainly it's artificial to restrict oneself to primitive concepts, unless of course you don't know about eigenvalues yet or forgot it all. :) And it is an exercise from the earliest chapter, so we're supposed to stay in simple-land. Did you look at my solution (http://news.ycombinator.com/item?id=3129023 http://news.ycombinator.com/item?id=3129023)? There's no higher-level theory in it. Is it brute force? Not sure. At least it doesn't require solving any element-wise equations.
- impendia 15y ago
  It's elegant, but as far as I can see, your argument only holds for the single matrix C which you describe.
  - gruseom 15y ago
    Oh, absolutely. The exercise is to construct one example. If you were talking about solving the general case (For any C, find D such that CD = -DC) I can see why you wanted more powerful tools.
    - impendia 15y ago
      oh! that's easier :)