here is a really simple program to swap 2 numbers without using a third variable.
say you have 2 numbers a and b;
now what you do is add a in b.
then save b-a in a.now save b-a in b.
{
int a=3,b=2;
cout<<"Initially to "<<a<<" "<<b;
{
b+=a;
a=b-a;
b=b-a;
}
cout<<"Swapped to "<<a<<" "<<b;
}
take care of the sequence.b takes a+b. now we put b in a by a=(b-a);meaning a=b(initial value).so now a=b-initial.so b=b-a..
simple.