2d数组指针 - 访问元素和地址

Question

我正在学习二维数组指针，这是我的代码。我不知道为什么这一行：

cout<<"Address of 1st part = "<<*ptr`  

当此行显示地址时，

未显示地址：

cout<<"Address of 1st part = "<<*(A)`  

这两行意味着同样可以帮助我。

#include <iostream>
using namespace std;


int main()
{
    int A[2][3]={{1,2,4},{5,8,3}};

    int *ptr;
    ptr=&A[0][0];

    cout<<"Address 1st part = "<<A<<endl;
    cout<<"Address 2nd part = "<<A+1<<endl;

    cout<<"Address 1st part = "<<ptr<<endl;
    cout<<"Address 2nd part = "<<ptr+1<<endl;

    cout<<"Address of 1st part = "<<*(A)<<endl;
    cout<<"Address of 1st part = "<<*ptr<<endl;

    cout<<"Address"<<*(A+1)+1<<endl;

    cout<<*(A+1)+2<<endl;

    return 0;
}

输出

Address 1st part = 0x7fffb6c5f660 
Address 2nd part = 0x7fffb6c5f66c 
Address 1st part = 0x7fffb6c5f660 
Address 2nd part = 0x7fffb6c5f664 
Address of 1st part = 0x7fffb6c5f660 
Address of 1st part = 1 
Address0x7fffb6c5f670 
0x7fffb6c5f674

Answer 1

这两行实际上并不相同。多维数组不等同于指向其基本类型的指针。

A的类型为int [2][3]，相当于int *[3]。 *A的类型为int[3]，而非int。连续的指向元素之间的步骤sizeof *A等于sizeof(int)*3。

ptr的类型为int *。 *ptr的类型为int。此处的步骤sizeof *ptr等于sizeof(int)。