题目如下：

The code in the main() function is incomplete. Write code as described in each of the comments marked (1), (2) and (3) above. Your code for (2) and (3) should take advantage of polymorphism to keep the code simple and short.

我的解法如下：（虽然解出来了，感觉有点蠢，之前并没有用到过 static_cast ）

重点是我觉得我的解法跟 polymorphism 多态好像没啥关系，是我的思路有问题吗？

#include <string> #include <iostream>  using namespace std;  // class definition for Quadraped class Quadruped{ protected:     int height; // height of the quadruped in hands public:     Quadruped(int height); // constructor     int get_height();  // get the height };  Quadruped::Quadruped(int hands){   // implementation of constructor     height=hands; }  int Quadruped::get_height(){  // implementation of get_height     return height; }  // ------------------------------------------------------------   // abstract class for Equines class Equine:public Quadruped{ public:     Equine(int hands); // constructor     virtual void ride() =0;  // not implemented here };  // constructor Equine::Equine(int hands):Quadruped(hands){     return; // nothing more to do }  // ------------------------------------------------------------   class Horse:public Equine{ public:     Horse(int hands); // constructor     virtual void ride();  // will define };  Horse::Horse(int hands):Equine(hands){     return; // nothing more to do }  void Horse::ride(){     cout << "You ride off into the sunset" << endl; }   // ------------------------------------------------------------  class Zebra:public Equine{ private:     int stripes; public:     Zebra(int hands); // constructor     virtual void ride();  // will define     void setStripes(int strs);     int getStripes(); };  Zebra::Zebra(int hands):Equine(hands){     stripes=0;     return; }   void Zebra::ride(){     cout << "The Zebra bites you and does not let go." << endl; }  void Zebra::setStripes(int strs) {     stripes=strs; }  int Zebra::getStripes() {     return(stripes); }  // ------------------------------------------------------------  int main(){     //collection of assets     int num=4;     Quadruped* my_things[num];      // complete the code below      // (1) add two horses and two zebras to my_things, all of different heights.      for (int i = 0; i < num; i++) {         if (i < 2) {             my_things[i] = new Horse(100 + i * 10);         } else {             my_things[i] = new Zebra(100 + i * 10);         }     }      // (2) call ride on each of the items in my_things      Equine * temp[num] ;      for (int i = 0; i < num; ++i) {          temp[i] = static_cast<Equine *>(my_things[i]);          temp[i]->ride();      }        // (3) add code to set the number of stripes on any zebras to 13.     for (int i = 0; i < num; ++i) {          if (typeid(*temp[i]).name() == typeid(Zebra).name()) {              Zebra * temp_zebra = static_cast<Zebra*>(my_things[i]);              temp_zebra->setStripes(13);              cout << temp_zebra->getStripes() << endl;                      }     }       // clean up      for (int i = 0; i < num ; ++i) {         delete temp[i];     }   } 

以上代码输出结果如下（ memcheck 没有内存泄漏）：