C++ Multidimensional array in existing memory

Question

(This is not a duplicate of this or this that refer to fixed sizes, the issue is not to understand how pointers are stored, but if the compiler can automate the manual funct

Answer 1

Based on this answer assuming you want an array of char you can do something like

std::vector x(1000);
char (&ar)[200][5] = *reinterpret_cast(x.data());

Then you can use ar as a normal two-dimensional array, like

char c = ar[2][3];