To answer your question, the first and third will probably be about the same speed. The second will be significantly slower (lots of memory), and the fourth will be obscenly complicated. If it's much slower or about the same (or even faster!) depends mostly on how (explicitly) parallel your brain is.
theorbtwo can't sleep either, but wasn't dreaming of code... as far as he remembers.
Warning: Unless otherwise stated, code is untested. Do not use without understanding. Code is posted in the hopes it is useful, but without warranty. All copyrights are relinquished into the public domain unless otherwise stated. I am not an angel. I am capable of error, and err on a fairly regular basis. If I made a mistake, please let me know (such as by replying to this node).