1: void f(int n);
2: void f(char* c);
3: f(NULL);
Based on the sample code above to ensure that the version
of f() that accepts a pointer is called on line 3 you change:
1) the definition of f on line 2 to void f(null*)
2) the definition of f on line 2 to void f(nullptr);
3) line 3 to f(char* NULL);
4)NULL on line 3 to std::nullptr_t;
5)the definition of f on line 1 to void f(int n<not_null>);

Пробовал реализовать в VS 2017, ни один из вариантов не компилируется, какой правльный