Swap 2 variable without 3 code example

Example 1: swap without using third variable

// SWAPPING WITHOUT USING THIRD VARIABLE
#include<stdio.h>  
 int main()    
{    
int a=10, b=20;      
printf("Before swap a=%d b=%d",a,b);      
a=a+b;//a=30 (10+20)    
b=a-b;//b=10 (30-20)    
a=a-b;//a=20 (30-10)    
printf("\nAfter swap a=%d b=%d",a,b);    
return 0;  
}

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