Switch 2 variables without using a 3rd variable in C++

#include 《iostream》

using namespace std;


int main()
{
	int a = 1;
	int b = 2;
	
	//before switch
	cout<< a<<endl;
	cout<<b<<endl;
	
	a = a+b;
	b = a-b; //this becomes b = a+b-b = 3-2 = 1
	a = a-b; // this becomes a = a+b-a = 3 - 1 = 2
	
	cout<<"After switch..."<<endl;
	
	//after switch
	cout<< a<<endl;
	cout<<b<< endl;
	
	return 0;
}