std::begin and std::end not working with pointers and reference why?

Question

Why std::begin() and std::end() works with array but not pointer[which is almost array] and reference of array [which is alias of original

Answer 1

Given just a pointer to the start of an array, there's no way to determine the size of the array; so begin and end can't work on pointers to dynamic arrays.

Use std::vector if you want a dynamic array that knows its size. As a bonus, that will also fix your memory leak.

The third case fails because, again, you're using (a reference to) a pointer. You can use a reference to the array itself:

int (&refOfFirst)[3] = first;

or, to avoid having to specify the array size:

auto & refOfFirst = first;

and begin and end will work on this exactly as they would work on first itself.