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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. class A
  5. {
  6. public:
  7.     int x;
  8.     int y;
  9.     virtual int add() = 0;
  10. };
  11.  
  12. class B
  13. {
  14. public:
  15.     int a;
  16.     int b;
  17.     virtual int sub() = 0;
  18. };
  19.  
  20. class C : public A, public B
  21. {
  22. public:
  23.     C() { x = 1; y = 2; z = 3; a = 4; b = 5; c = 6; }
  24.     int c;
  25.     int z;
  26.     virtual int add() { return a + z; }
  27.     virtual int sub() { return c - x; }
  28.     int mul() { return b * y; };
  29. };
  30.  
  31. class D : public A, public B
  32. {
  33. public:
  34.     D() { x = 1; y = 2; z = 3; a = 4; b = 5; c = 6; }
  35.     int c;
  36.     int z;
  37.     virtual int add() { return a + z; }
  38.     virtual int sub() { return x - c; } // sub 做的事情不一樣
  39.     int mul() { return b * y; };
  40. };
  41.  
  42. int main()
  43. {
  44.     A *p = new D; // 這裡視情況可能建立 C 或 D
  45.     cout << p->add() << endl;
  46.     cout << ((C *)p)->sub() << endl;
  47.     cout << ((C *)p)->mul() << endl;
  48. }
  49.  
Success #stdin #stdout 0.01s 2856KB
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https://ideone.com/RUFzz
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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