Swap two numbers without using a third variable

How to swap two numbers using third variable ?? 

Here are five different ways of doing it..

void main(){

int a=5,b=10;

//#1

a=b+a;

b=a-b;

a=a-b;

printf("a= %d, b= %d\n",a,b);

//#2

a=5;

b=10;

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

printf("a= %d, b= %d\n",a,b);

//#3

a=5;

b=10;

a=b-~a-1;

b=a+~b+1;

a=a+~b+1;

printf("a= %d, b= %d\n",a,b);

//#4

a=5;

b=10;

a=a^b;

b=a^b;

a=b^a;

printf("a= %d, b= %d\n",a,b);

#5

a=5;

b=10;

a=b+a,b=a-b,a=a-b;

printf("a= %d, b= %d\n",a,b);

}

Note: Please note carefully the difference between #1 and #5.