How to understand the application of multi-dimensional array pointer

Question

Hi all How to understand the application of multi-dimensional array pointer in c plus plus. thanks in advance.

Vulpes · Answer

This simple example may help: // create and initialize a 2 x 2 array of ints int array2d[2][2]; array2d[0][0] = 1; array2d[0][1] = 2; array2d[1][0] = 3; array2d[1][1] = 4; // traverse using pointer int *p = (int *)array2d; for(int i = 0; i // access element [1][1] using pointer int e = *(p + 2 * 1 + 1); printf(%d
 e); // 4 return 0; Traversing the array using a pointer works because the rows of the multidimensional array are stored one after the other in memory. In general you can access the [i][j]th element of the array by adding: (row length) * i + j to a pointer to the first element and then dereferencing the resulting pointer.

Ken H · Answer

hi sam hobbs thanks for your help.

Sam Hobbs · Answer

Multi-dimensional arrays in C can be confusing. I think that if you use one syntax then the items are stored so that all items of a row are contiguous but then if you use a different syntax then all items of a column are contiguous. A better solution is to use C++ vectors but the C++ standard did not have specific support for multi-dimensional vectors. There are many articles in other sites and forum answers in other forums showing how to do that. I know I asked about this in the MSDN forums. I don't know about the new C++ language standard but I sure hope that it has better support for multidimensional arrays although tecnically they are probably multidimensional vectors. If you must do it the C way then see Ted Jensen's Tutorial on Pointers and Arrays in C .

Ken H · Answer

thanks!