diamond inheritance problem in c++ and its solution code example

Example 1: Diamond inheritance

The "diamond problem" (sometimes referred to as the "Deadly Diamond of Death") is an ambiguity that arises when two classes B and C inherit from A, and class D inherits from both B and C
If there is a method in A that B and C have overridden, and D does not override it, then which class of the method does D inherit: that of B, or that of C?

Example 2: c++ multiple inheritance diamond problem

class Parent;
class a : virtual public Parent; //add virtual
class b : virtual public Parent; //add virtual
class c : public a, public b;