namespace test
{
    using System;
    class Program
    {
        static void Main(string[] args)
        {
         

int a, b;
  a = 100;
  b = -9990;
int c;
  DateTime dt = DateTime.Now;
  for (int i = 0; i < 10000000; i++)
  {
  a = a + b;
  b = a - b;
  a = a - b;
  }
  int time1 = (DateTime.Now - dt).Milliseconds;
  dt = DateTime.Now;
  for (int i = 0; i < 10000000; i++)
  {
  c= a;
  a = b;
 b = c;
  }
  int time2 = (DateTime.Now - dt).Milliseconds;
dt = DateTime.Now;// 你漏了这一行了
  for (int i = 0; i < 10000000; i++)
  {
  b = a + 0 * (a = b);
  }
  int time3 = (DateTime.Now - dt).Milliseconds;
  Console.WriteLine(time1);
  Console.WriteLine(time2);  
  Console.WriteLine(time3);
  Console.ReadLine();

        }
    }
}