Remove Adjacent Duplicates

Write a function string removeAdjacent(const string& s) that uses a stack<char> to repeatedly delete pairs of equal adjacent characters until no such pair remains, and returns whatever is left.

Example: "abbaca" — "bb" cancels leaving "aaca", then "aa" cancels leaving "ca". The test prints the returned string on its own line (see Expected Output).

If every character cancels, return the empty string; the test then prints the line (empty).

Do NOT write a main function.