Group Shifted Strings

Group strings by a shift-invariant key rather than comparing every pair. For a nonempty string, subtract the first character from each character modulo 26 and serialize those offsets. For example, abc and bcd both normalize to offsets 0,1,2; wrapping is handled because (current - first + 26) % 26 stays in 0 through 25. Store each original string in a hash map keyed by that normalized sequence. This is more reliable than using only adjacent differences unless you define the representation consistently. Preserve original strings in the output because the signature is only an equivalence key. Ask whether case and non-letters are allowed before assuming lowercase English letters. Test empty strings, single letters, az versus ba, repeated characters, and multiple groups with the same length. Building keys is O(total characters) time and storage, aside from output.