[R] Simple list manipulation question

[Sean Davis]

I have a list of vectors

$A
"AB" "BC" "CD"

$B
"GF" "HG" "FH" "FJ"

and I want to convert it into a dataframe of form

A  AB
A  BC
A  CD
B  GF
B  HG
B  FH
B  FJ

Just can't quite come up with a nice "R" solution for it.

Thanks,
Sean