二级指针

二级指针

void swap1(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

void swap2(int **a, int **b) {
    int t = **a;
    **a = **b;
    **b = t;
}

// 高级一点使用void**只是为了通用，可以交换各种类型
void swap3(void **a, void **b)
{
    void *t;
    t =*a;
    *a =*b;
    *b=t;
}

int main(int argc, char **argv) {
    int a, b;
    a = 16;
    b = 32;
    swap1(&a, &b);

    printf("a=%d,b=%d \n", a, b);

    int i = 3;
    int j = 5;
    int *p = &i;
    int *q = &j;
    printf("before *p=%d,*q=%d \n", *p, *q);
    swap2(&p, &q);
    printf("after *p=%d,*q=%d \n", *p, *q);

    char *s1="abc";
    char *s2="def";
    swap3((void**)&p, (void**)&q);

    swap3((void**)&s1, (void**)&s2);

    printf("after s1=%c,s2=%c \n", *s1, *s2);

}