How to Exchange Two Variables without Others

This is a funny question for me, so I list three methods to solve it.

1.
#include

using namespace std;

int main()
{
    int i, j;
    cin >> i >> j;

    i ^= j;
    j ^= i;
    i ^= j;

    cout << i << j;

    return 0;
}

2.
#include

using namespace std;

int main()
{
    int i, j;
    cin >> i >> j;

    i = i + j;
    j = i - j;
    i = i - j;

    cout << i << j;

    return 0;
}

3.
#include

using namespace std;

int main()
{
    int i, j;
    cin >> i >> j;

    i = i + j - (j = i);

    cout << i << j;

    return 0;
}