Swapping Two Numbers without using a Third Variable

This is a very small example which demonstrates swapping 2 numbers.We all know how to swap two numbers with the help of a third variable. What i would like to share here is to do the same swapping with the help of two numbers.

 Please find the attached source code for the complete reference.

 
static void Main(string[] args)

{

      //Swap 2 numbers without a third variable

      int a = 10;

      int b = 20;            

      Console.WriteLine("Values before Swapping...");

      Console.WriteLine("a = {0} ; b={1}",a,b);

      a = a + b; 

      b = a - b;

      a = a - b;

     Console.WriteLine("Values After Swapping...");

     Console.WriteLine("a = {0} ; b={1}",a,b);

     Console.ReadLine();

}

 

In the above sample i have hard coded 2 integers with values a=10 and b=20.

 

Logic explanation

 

First step is a= a+b ; Now a holds value 30.

 

Second step: b=a-b; Now b holds value (30-20) =10;

 

Third step : a=a-b; Now a holds value (30-10) = 20;

 

Values before swapping :

a= 10;

b=20;

 

Values after swapping:

a=20;

b=10; 

 

So in three simple steps we have achieved the desired result.