How to swap two numbers without using temp variables or arithmetic operations?

Question

This equation swaps two numbers without a temporary variable, but uses arithmetic operations:

a = (a+b) - (b=a);

How can I do it without ar

Answer 1

I haven't seen this C solution before, but I'm sure someone has thought of it. And perhaps had more posting self-control than I do.

fprintf(fopen("temp.txt", "w"), "%d", a);
a = b;
fscanf(fopen("temp.txt", "r"), "%d", &b);

No extra variables!

It works for me, but depending on the stdio implementation you may have to do something about output buffering.