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

Using XOR,

void swap(int &a, int &b)
{
    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
}

One liner with XOR,

void swap(int &a, int &b)
{
    a ^= b ^= a ^= b;
}

These methods appear to be clean, because they don't fail for any test-case, but again since (as in method 2) value of variable is modified twice within the same sequence point, it is said to be having undefined behavior declared by ANSI C.