递归Factorial.

OOP/test.cpp

@@ -3,68 +3,18 @@ using std::cout;
 using std::cin;
 using std::endl;
 
-class A {
-protected:
-    int a;
-
-public:
-    A(int _a) : a(_a) {
-    }
-    void display() {
-        std::cout << a << std::endl;
-    }
+template <int x>
+struct Factorial {
+    static const unsigned long long value = x * Factorial<x-1>::value;
 };
 
-class B : virtual public A {
-protected:
-    int b;
-
-public:
-    B(int _a, int _b) : A(_a+1), b(_b) {
-    }
-    void display() {
-        A::display();
-        std::cout << b << std::endl;
-    }
+template <>
+struct Factorial<0> {
+    static const unsigned long long value = 1;
 };
 
-class C : virtual public A {
-protected:
-    int c;
-
-public:
-    C(int _a, int _c) : A(_a + 2), c(_c) {
-    }
-    void display() {
-        A::display();
-        std::cout << c << std::endl;
-    }
-};
-
-// class D : public B, public C {
-// protected:
-//     int d;
-
-// public:
-//     D(int _a, int _b, int _c, int _d) :A(_a), B(_a, _b), C(_a, _c), d(_d){};
-
-//     void display() {
-//         A::display();
-//         B::display();
-//         C::display();
-//         std::cout << d << std::endl;
-//     }
-// };
-
 int main() {
-    // D objD(1, 2, 3, 4);
-    // objD.display();
-    // cout << "---\n" << sizeof(A) << endl << sizeof(B) << endl << sizeof(C) << endl;
-    // cout << -13 % 6 << endl;
-    cout << "---";
-    endl(cout);
-    endl(cout);
-    cout << "---";
-    endl(cout);
+    Factorial<20> a;
+    cout << a.value << endl;
     return 0;
 }