What i want is to first store the given input as follows :-
and then make a check if the pair is present in particular subset of a set.
For e.g if the user can give index 0 and pair {B,C} we need to search the first index value i.e {{A,B},{B,C},{C,D}} and return true or false based on its presence. What data structure i should use. I tried vector but not helping me
Kindly help