update dir

struct/ext_struct_func.cpp

@@ -0,0 +1,28 @@
+#include<iostream>
+#include<stdio.h>
+
+struct Base {         
+    int v1;
+//    private:   //error!
+        int v3;
+    public:   //显示声明public
+        int v2;
+    virtual void print(){       
+        printf("%s\n","Base");
+    };    
+};
+
+struct Derived:Base {         
+
+    public:
+        int v2;
+    void print(){       
+        printf("%s\n","Derived");
+    };    
+};
+
+int main() {
+    Base *b=new Derived();
+    b->print();
+    return 0;
+}