Complementing a Strand of DNA

In DNA strings, symbols 'A' and 'T' are complements of each other, as are 'C' and 'G'.

The reverse complement of a DNA string s is the string s^c formed by reversing the symbols of s, then taking the complement of each symbol (e.g., the reverse complement of "GTCA" is "TGAC").

Given: A DNA string s of length at most 1000 bp.

Return: The reverse complement s^c of s.