交换变量值的5种方法

#include <stdio.h>

#define swap_macro_0(a, b) 
    do { 
            typeof(a) c; 
            c = a; 
            a = b; 
            b = c; 
    } while(0)

#define swap_macro_1(a, b) 
    do { 
            a = a + b; 
            b = a - b; 
            a = a - b; 
    }while(0)

#define swap_macro_2(a, b) 
    do { 
            a = a ^ b; 
            b = a ^ b; 
            a = a ^ b; 
    }while(0)

#define swap_macro_3(a, b) 
    do { 
           a = a * b; 
           b = a / b; 
           a = a / b; 
    }while(0);
    
#define swap_macro_4(a, b) 
    do { 
            a = a + b - (b = a); 
    }while(0);
    
int main()
{
    int type, a, b;
    
    scanf("%d, %d, %d", &type, &a, &b);
    printf("before a = %d, b = %d
", a, b);
    switch(type)
    {
        case 0:
            {
                swap_macro_0(a, b);
                break;
            }
        case 1:
            {
                swap_macro_1(a, b);
                break;
            }
        case 2:
            {
                swap_macro_2(a, b);
                break;
            }
        case 3:
            {
                swap_macro_3(a, b);   
                break;      
            }
        case 4:
            {
                swap_macro_4(a, b);   
                break; 
            }
        default:
            {
                printf("unknown swap type!
");
                return 0;
            }
    }
    printf("after a = %d, b = %d
", a, b);
    return 0;
}