Variation of the dining philosophers: is the standard solution still valid? I have a problem that is almost equal to the standard one of the dining philosophers, but has a quirk: while a philosopher thinks, he still holds the fork on his left.

If after the period of thinking (which isn't infinite), I release the fork on the left and then apply the normal solution (that is, acquire forks in the order of their priority), then would this solution be correct for this problem?
If the philosopher eats (holding both forks), drops the right fork and thinks for a while, and then drops the left fork to take a nap (or something similar), it is just the original problem: Each philosopher must ensure getting both forks without deadlock. Take a look at Allen B. Downey's "The Little Book on Semaphores" for in-depth discussion (this problem is hard!).