using pointers to display elements from a multidimensional array

Question

Hi Im just starting to get my head around pointers and arrays and Ive more or less know how to manipulate pointers in a one dimensional arrays to display the elements. But how about in multidimensional arrays? I have been practicing with this code:

#include<iostream>
using namespace std;
int main()
{

    int a[2][3]= { {1,2,3},{4,5,6}};
    int (*ptr)[3] = &a[0]; // or (*ptr)[3] = a;

    cout <<"Adress 0,0: "<< a << endl;
    cout <<"Adress 0,0: "<< ptr << endl;         
    cout <<"Value 0,0: "<< *a[0] << endl;
    cout <<"Value 0,0: "<< *(ptr)[0]<< endl;
    cout <<"Adress 0,1: "<< &a[0][1] << endl;
    cout <<"Adress 0,1: "<< (ptr)[1] << endl;       

    return 0;
}

I have managed to display the address and value of a[0][0] using the array name and the pointer, but how to display the address and value of a[0][1] and the succeeding elements by using the pointer?

Answer 1

(ptr)[1] (same as ptr[1] ) doesn't point to a[0][1] , it points to a[1][0] because you defined ptr as a pointer to int[3] , not int . Therefore incrementing ptr by 1 with ptr[1] skips three int s, up to a[1][0] .

To increment ptr by the size of one int instead of three int s:

ptr[0] + 1

The above will point to a[0][1] . And to access that:

*(ptr[0] + 1)

Answer 2

    #include<iostream>
    using namespace std;

    int main()

{

    int a[2][3]= { {1,2,3},{4,5,6}  };
    int (*ptr)[3] = &a[0]; // or (*ptr)[3] = a;

    cout <<"Adress 0,0: "<< a << endl;
    cout <<"Adress 0,0: "<< ptr << endl;         
    cout <<"Value 0,0: "<< *a[0] << endl;
    cout <<"Value 0,0: "<< *((ptr)[0]+0)<< endl;
    cout <<"Adress 0,1: "<< &a[0][1] << endl;
    cout <<"Adress 0,1: "<< (ptr)[0]+1 << endl;       
    cout <<"value 0,1: "<<  a[0][1] << endl;
    cout <<"value 0,1: "<< *((ptr)[0]+1) << endl;

    cout <<"Adress 1,0: "<< &a[1][0] << endl;
    cout <<"Adress 1,0: "<< (ptr)[1] << endl;       
    cout <<"value 1,0: "<<  a[1][0] << endl;
    cout <<"value 1,0: "<< *((ptr)[1]+0) << endl;       

    return 0;
}

Hope this clears your doubt.