C++學習筆記（6）

1、多級指針

int main()
{
    int a[] = {1, 2, 3};
    int b[] = {4, 5, 6};
    int c[] = {7, 8, 9};
    //指針數組是特殊的二維數組
    int* arr[] = {a, b, c};
    //指針數組相當於二級指針
    int** p = arr;
    //a[0][1]
    printf("%d\n", *(*p + 1));
    //a[2][1]
    printf("%d\n", *(*(p + 2) + 1));

    return 0;
}

2、值傳遞和地址傳遞

int main1()
{
    int a = 1;
    int b = 2;
    printf("%p,%p\n", &a, &b);
    //值傳遞
    swap(a, b);
    printf("%d,%d\n", a, b);
    printf("%p,%p\n", &a, &b);
}

void swap1(int a, int b)
{
    int temp = a;
    a = b;
    b = temp;
    printf("%p,%p\n", &a, &b);
}
/****************************/
int main2()
{
    int a = 1;
    int b = 2;
    printf("%p,%p\n", &a, &b);
    //指針
    swap2(&a, &b);
    printf("%d,%d\n", a, b);
    printf("%p,%p\n", &a, &b);
}

void swap2(int* aa, int* bb)
{
    //改變內存地址對應的值
    int temp = *aa;
    *aa = *bb;
    *bb = temp;
    printf("%p,%p\n", &aa, &bb);
}

3、數組名做函數參數【函數的形參會退化爲指針】

int main()
{
	int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
	int n = sizeof(a) / sizeof(a[0]);

	//數組名做函數參數
	printArrary(a, n); 
	return 0;
}


void printArrary(int *a, int n)//數組的指針爲此數組第一個元素的內存地址
{
	int i = 0;
	for (i = 0; i < n; i++)
	{
		printf("%d, ", a[i]);
	}
	printf("\n");
}

//TODO day06(09指針作爲函數返回值)