The solutions

   return  a ^  b ? c : a
   return  a == b ? a : c

Are expressing exactly the same idea- When A and B are identical, they will xor to 0, and otherwise something nonzero. Thus, xor can be thought of in general as a "!=" operator, provided booleans work like you'd expect in C.

Thank you for your remind. We have corrected the error. Yes, you are right, these two solutions have the same logic.