交换a，b两个数；

//常规方法加减法
include<stdio.h>
include<stdlib.h>
int main()
{
 int a = 10;
 int b = 20;
 a = a + b;
 b = a - b;
 a = a - b;
 printf("%d %d\n", a, b);
 system("pause");
 return 0;
 }
 //按位异或法，异或二进制位数
 include<stdio.h>
 include<stdlib.h>
int main()
{
 int a = 10;
 int b = 20;
 a = a^b;
 b = a^b;
 a = a^b;
 printf("a = %d,b = %d\n", a, b);
 system("pause");
 return 0;
}
//常规方法 定义中间变量
 include<stdio.h>
 include<stdlib.h>
int main()
{
 int a = 10;
 int b = 20;
 int tmp = 0;
 tmp = a;
 a = b;
 b = tmp;
 printf("a = %d,b = %d\n", a, b);
 system("pause");
 return 0;
}