The grammar S \(\to\) aSa|bS|c is

Key insight: the three alternatives for S start with different terminals, so one-token lookahead suffices.

• Compute FIRST sets for the alternatives of S:

  • aSa has FIRST = {a}

  • bS has FIRST = {b}

  • c has FIRST = {c}

• Because these FIRST sets are pairwise disjoint, a single lookahead token determines which production to use, so the grammar is LL(1).

• Every LL(1) grammar is also LR(1), so the grammar is LR(1) as well.

Therefore the correct characterization is: Both LL(1) and LR(1).