Check out the pair of cortices on that one.

i think she had a graph theory one as well

I'm kind of relieved to see Vi Hart screw up, though.

I too like it when exceptionally smart people make mistakes.

A stab at the snake grammar... first let's see if angle brackets work >

I was never great at these. I think some of the εs are redundant. This also doesn't include "straight" (S here means start).
S -> L | R | ε
L -> LM | l | ε
R -> RT | r | ε
M -> LR | R | ε
T -> RL | L | ε

Line one reads: "S yields L or R or ε". ε is the empty string.

Uppercase are variables, lowercase are terminals. Start with S, and replace it with either L or R (or ε, which is like erasing it). Keep doing those kinds of replacements until there are no variables left. The resulting lowercase string should be a valid slither.

As for an algorithm... if you have this kind of grammar then the algorithm has a boring general solution, and google can provide it :)

snakesnakesnakesnakesnake

Dammit, that was supposed to be a reply to Spiteful Crow.

Charmingly autistic.

She did. You never talked to her. She was there the whole time.

^
*****