Key points#

• Basic
  • Reference and Pointer
  • Constructor and Destructor
  • Inheritance & Polymorphism
  • Static
  • STL
• Programming
  • Inherit and virtual
  • Defining method/function
  • Template
  • IO Stream
  • Smart pointer
  • Overriding andOverloading
  • Compile guard

Consolidation1#

• What are the main features of the Object-Oriented?
  • Encapsulation
  • Inheritance
  • Polymorphism
• How to describe these features?

What is not correct about the derived class?
[This question has multiple correct answers. You must select all correct answers.]
(A) A derived class can inherit any member function of the base class.

可以继承，但继承下来的东西不一定所有的都能用

(B) Derived class can override all existing member functions of the base class.

Need virtual and override

(C) Derived classes can have their own new members.
(D) Derived classes cannot initialize data members of the base class.
(E) A derived class can be a base class of another class.

Wrapping data and its related functionality into a single entity is known as:
(A) Abstraction.
(B) Encapsulation.
(C) Inheritance.
(D) Polymorphism.
(E) Modularity.

Consolidation2#

• How to reuse the code effectively?
  • Use .h
• How to implement a template class?

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template <typename T> class Name {
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    Name<T>;
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}

• How to avoid compile conflict?
  • Use compile guard: avoid compile the same code multiple times

Which of the following user-defined header file extensions is used in C++?
(A) .dll
(B) .cpp
(C) .h
(D) .header
(E) .obj

dll: dynamic linked library

Consolidation3#

• What is the difference between the reference and the pointer?
• When would we use a reference or pointer as the parameter of a function/method?

Which of the following statements is not correct in relation to reference?
(A) Reference is the alternate name of the object.
(B) Reference is the alternate name of the variable.
(C) Cannot create an array of references.
(D) A reference value once defined can be reassigned.
(E) A reference value once defined cannot be reassigned.

Consolidation4#

• What is the features of the stream?
• When would we use ostream or istream?
• How to use the operator << and >> flexibly?

Which of the following statements are correct in terms of the cin and the cout?
[This question has multiple correct answers. You must select all correct answers.]
(A) cin and cout are commands that are used to input and output.
(B) cin is the object of istream class, and cout is the object of ostream class.
(C) cin and cout are standard library functions defined in the iostream library file.
(D) cin and cout are standard objects defined in the iostream library file.
(E) The cin object corresponds to the standard input stream, the cout object corresponds to the standard output stream.

Consolidation5#

• What is the features of the smart pointer?
• When would we use smart pointer?
• What is the different between the unique_ptr and shared_ptr?

Which of the following statements is correct in relation to smart pointer?
(A) Smart pointer is a class object that acts like a pointer but has additional features.
(B) We can construct different unique_ptr to the same object.
(C) We can copy a unique_ptr but cannot construct any other unique_ptr to the same object.
(D) The object to which one shared_ptr points should be released after the shared_ptr is used out.
(E) The auto_ptr is not one of smart pointers.

Consolidation6#

• What are the features of the constructor and the destructor?

What will be the output of the following C++ program?

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#include <iostream>
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using namespace std;
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class A{
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public:
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    A(){ cout<<"Constructor called\n"; }
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    ~A(){ cout<<"Destructor called\n"; }
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};
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int main(int argc, char const *argv[]) {
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    A *a = new A[4];
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    delete[] a;
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    return 0;
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}

Consolidation7#

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template <typename T> class Area {
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public:
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    void setLength(T newValue);
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protected:
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    T length;
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};

• How to implement the statement of the template method setLength()?
• How to implement two different template methods of the class Area, that can calculate the area of a square which uses length to be the side length.

Consolidation8#

• Your program performs the operation:

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int x;
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std:: ifstream fileStream(“test.txt”);
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fileStream >> x;

• What will happen if the content of the file is not a number, and how to fix your program?

Consolidation9#

• What is the difference between overloading and overriding?
• How to implement the overloading and overriding?
• What is the purpose of using a static data?

Please find out the bugs that existed in the following programs.

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class Animal {
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public:
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    static num;
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    Animal(int _a);
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    int age;
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    virtual void noise()=0;
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};
8

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Animal::Animal(int _a) :age(_a){num++;}
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void Animal::noise(){
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    cout<<"animal voice"<<endl;
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}
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class Dog : public Animal {
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public:
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    Dog();
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    void noise() override;
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    voideat(int bone);
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};
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Dog::Dog(): Animal(1){num++;}
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void Dog::noise() {
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    cout<<"wang"<<endl;
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}
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voidDog::eat(int bone){
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    cout<<bone<<endl;
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}
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class Cat: public Animal{
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public:
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    Cat();
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    void noise() override;
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    voiddrink();
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};
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void Cat::noise() {
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    cout<<"miao"<<endl;
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}
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voidCat::drink(){
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    cout<<"drink water"<<endl;
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}
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void bark(Animal *a){
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    a->noise();
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}
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int main()
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{
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    Animal a(0);
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    Animal * pa= new Animal(1);
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    Animal * pd= new Dog(10);
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    pd->noise(); pd->eat(10);
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    Animal * pc= new Cat();
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    pc->noise(); pc->drink();
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    Dog d(10); Cat c();
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    d.noise(); d.eat();
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    c.noise(); c.drink();
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    bark(d); bark(c);
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    cout<<d.num<<endl;
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    cout<<Animal::num<<endl;
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    return 0;
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}

Consolidation10#

• What is the difference between the value way and the reference way when defining the variable/object?
• What are the advantages and disadvantages of using a pointer to access the variable or object?
• What is the difference in the ways of allocating and releasing the memory manually in C and C++?

What are the advantages of using pointers to access variables/objects?
[This question has multiple correct answers. You must select all correct answers.]
A. Support dynamic memory allocation
B. Enable flexible manipulation of memory addresses
C. Enable flexible access to different objects by using the same pointer.
D. Avoid copying large objects (directly access the original data)
E. Eliminate the risk of null pointer dereferencing

Note#

• Please review all the weekly exercises’ solutions.