swap two numbers 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: swap 2 integers without using temporary variable

using System;

class MainClass {
  public static void Main (string[] args) {
    int num1 = int.Parse(Console.ReadLine());
    int num2 = int.Parse(Console.ReadLine());
      num1 = num1 + num2; 
      num2 = num1 - num2; 
      num1 = num1 - num2; 
      Console.WriteLine("After swapping: num1 = "+ num1 + ", num2 = " + num2); 
    Console.ReadLine();
  }
}