如何交换两个数字

//几种经典的交换两个数方法.

#include <stdio.h>

void function1(int *a, int *b) {   //可能产生溢出错误
    *a = *a + *b;
    *b = *a - *b;
    *a = *a - *b;
}

void function2(int *a, int *b) {  //位运算 ,不能和自身交换
    *a ^= *b;
    *b ^= *a;
    *a ^= *b;
}

void function3(int *a, int *b) { //最正常的写法
    int t;
    t = *a;
    *a = *b;
    *b = t;
}


int main()
{
    int a=8,b=9;
    printf("Before exchange,a is %d,b is %d \r\n",a,b);
    //使用两个寄存器的写法
    __asm {         
        MOV EAX,a
        MOV EBX,b
        MOV a,EBX
        MOV b,EAX
    }
    printf("After exchange,a is %d,b is %d \r\n",a,b);

    
    //使用一个寄存器的写法
    __asm {         
        MOV EDX,b
        XCHG EDX,a
        MOV b,EDX
    }
    printf("After exchange,a is %d,b is %d \r\n",a,b);

    //使用一个寄存器的写法
    __asm {
        MOV ECX,a
    }
    a=b;
    __asm{
        MOV b,ECX
    }
    printf("Before exchange,a is %d,b is %d \r\n",a,b);

    function1(&a, &b);
    printf("After exchange,a is %d,b is %d \r\n",a,b);

    function2(&a, &b);
    printf("Before exchange,a is %d,b is %d \r\n",a,b);

    function3(&a, &b);
    printf("After exchange,a is %d,b is %d \r\n",a,b);

    getchar();
    
    return 0;

}