Which of the following lines correctly declare a f

Which of the following lines correctly declare a function which processes/modifies an input pointer?

void Init(int**  ptr);  //1
void Init(int*   ptr);  //2
void Init(int*& ptr);  //3
void Init(int&* ptr);  //4

Explanation

1. Correct. The function accepts a pointer to pointer, which, when dereferenced, returns the original pointer we want to modify.
2. Wrong. The function creates a copy of the input variable, in this case - a copy of the input pointer, hence the original input pointer is not modified.
3. There are no pointers to references in C++.
4. Correct. The function accepts a reference to original pointer at input, and is able to modify it.