program to swap two numbers code example

Example 1: Write a program to show swap of two numbers without using third variable.

#include  
 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 values in variables in c

#include 
#include 

int main()
{
  	//initialize variables
	int num1 = 10;
	int num2 = 9;
  	int tmp;
  	
  	//create the variables needed to store the address of the variables
  	//that we want to swap values
  	int *p_num1 = &num1;
  	int *p_num2 = &num2;
  
  	//print what the values are before the swap
  	printf("num1: %i\n", num1);
    printf("num2: %i\n", num2);
  
  	//store one of the variables in tmp so we can access it later
  	//gives the value we stored in another variable the new value
  	//give the other variable the value of tmp
  	tmp = num1;
  	*p_num1 = num2;
  	*p_num2 = tmp;

  	//print the values after swap has occured
   	printf("num1: %i\n", num1);
    printf("num2: %i\n", num2);
  	
	return 0;
}