预测以下C++程序的输出。
问题1
C
#include
#include
using namespace std;
class String
{
char *p;
int len;
public:
String(const char *a);
};
String::String(const char *a)
{
int length = strlen(a);
p = new char[length +1];
strcpy(p, a);
cout << "Constructor Called " << endl;
}
int main()
{
String s1("Geeks");
const char *name = "forGeeks";
s1 = name;
return 0;
}
CPP
#include
using namespace std;
class A
{
public:
virtual void fun() {cout << "A" << endl ;}
};
class B: public A
{
public:
virtual void fun() {cout << "B" << endl;}
};
class C: public B
{
public:
virtual void fun() {cout << "C" << endl;}
};
int main()
{
A *a = new C;
A *b = new B;
a->fun();
b->fun();
return 0;
}
输出:
Constructor called
Constructor called
输出的第一行由语句“ String s1(“ Geeks”);”打印。第二行由语句“ s1 = name;”打印。第二次调用的原因是,单个参数构造函数还可以用作转换运算符(有关详细信息,请参见此内容)。
问题2
CPP
#include
using namespace std;
class A
{
public:
virtual void fun() {cout << "A" << endl ;}
};
class B: public A
{
public:
virtual void fun() {cout << "B" << endl;}
};
class C: public B
{
public:
virtual void fun() {cout << "C" << endl;}
};
int main()
{
A *a = new C;
A *b = new B;
a->fun();
b->fun();
return 0;
}
输出:
C
B
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