adding the diamond problem

lectures/26_inheritance_II/diamond_test2.cpp

@@ -0,0 +1,32 @@
+#include <iostream>
+
+class Human {
+public:
+    Human() { std::cout << "Human constructor\n"; }
+};
+
+// The virutal keyword tells the compiler: 
+// "Hey, if this class is used in a diamond-like hierarchy, only one shared Human base should exist, no matter how many paths lead to it."
+// The compiler then: Makes sure that only one instance of Human exists inside CSStudent.
+class Student : virtual public Human {
+public:
+    Student() { std::cout << "Student constructor\n"; }
+};
+
+class Worker : virtual public Human {
+public:
+    Worker() { std::cout << "Worker constructor\n"; }
+};
+
+class CSStudent : public Student, public Worker {
+public:
+    CSStudent() { std::cout << "CSStudent constructor\n"; }
+};
+
+// problem with this program: Human constructor runs twice!
+int main() {
+    // CSStudent has two copies of Human, one via Student and one via Worker.
+    // Ambiguity: If we try to access a Human member from CSStudent, the compiler doesn’t know which one we mean.
+    CSStudent cs;
+    return 0;
+}