二維數組指針 - 訪問元素和地址

Question

我正在學習2d數組指針，這裏是我的代碼。我DONOT知道爲什麼這條線：

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

沒有顯示，而這條線給我看地址的地址：

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

這兩條線是指同任何一個可以幫助我。

#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; 
} 

輸出

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

這兩行實際上並不意味着同樣的。多維數組不等於指向其基本類型的指針。

A類型爲int [2][3]，相當於int *[3]。 *A的類型是int[3]，而不是int。連續指向元素sizeof *A之間的步長等於sizeof(int)*3。

ptr的類型爲int *。 *ptr的類型是int。此處的步驟sizeof *ptr等於sizeof(int)。