swap two number code example

Example 1: swap 2 numbers without using 3rd variable

a=10;
b=20;
a=a+b;//a=30 (10+20)    
b=a-b;//b=10 (30-20)    
a=a-b;//a=20 (30-10)

Example 2: how to swap 2 numbers without 3rd variable

int a = 3;
int b = 5;
a = b*a;
b = a/b
a = a/b