C++笔试题2

C++笔试题（第2套）
时间：20分钟 总分：100分（第1题每小题2分，其余每题10分）
姓名： 分数：

1. C++有很多关键字，其中
   ① 自动类型推导的关键字是____________
   ② 外部变量声明的关键字是____________
   ③ 显式重写虚函数的关键字是____________
   ④ 抛出异常的关键字是____________
   ⑤ 模板定义的关键字是____________

int main() {
int a = 5, b = 10;
int &ref = a;
ref = b;
std::cout << a << " " << b;
return 0;
}
//如上输出为____________

3. 在64位平台下，

void fun(char arr[])
{
  cout << sizeof(arr);
}
int main(){
char arr[] = "12345";
cout << sizeof(arr);	// ①
fun(arr);	        // ②
return 0;
}
//如上①②输出分别为____________

int main() {
    unsigned char a = 255;
    a = a + 1;
    cout << (int)a;
    return 0;
}
//程序的输出是____________

int main() {
    int arr[3] = {10, 20, 30};
    __________________________ // 补全代码使下一行输出结果为10,20,30
    cout << p[-1] <<”,”<< *p <<”,”<< *(p + 1);
}

class Widget {
    static int count;
    int id;
public:
    Widget() : id(++count) { cout << "C" << id; }
    ~Widget() { cout << "D" << id; }
};
int Widget::count = 0;

int main() {
    Widget w1;
    Widget* w2 = new Widget();
    delete w2;
}
//如上程序的输出是____________

class Base {
public:
    virtual void show() { cout << "Base"; }
};
class Derived : public Base {
public:
    void show() override final { cout << "Derived"; }
};
class Child : public Derived {
public:
    void show() override { cout << "Child"; }
};
//请指出如上程序中的问题____________              

template<int N>
struct Factorial {
    static const int value = N * Factorial<N-1>::value;
};

template<>
struct Factorial<0> {
    static const int value = 1;
};

int main() {
    cout << Factorial<5>::value;
}
//如上输出结果是____________

class Resource {
public:
    Resource() { cout << "R "; }
    ~Resource() { cout << "~R "; }
};

int main() {
    auto p1 = make_shared<Resource>();
    auto p2 = p1;
    weak_ptr<Resource> wp = p1;
    p1.reset();
    cout << (wp.expired() ? "Y" : "N");
    p2.reset();
    cout << (wp.expired() ? "Y" : "N");
}
//如上输出结果是____________

10. Lambda表达式

int main() {
    int counter = 0;
    auto f = [counter]() mutable {
        cout << ++counter;
    };
    f();
    f();
    cout << counter;
}
//如上输出结果是____________