有一个图书类，能够借书和还书。将如下程序补充完整，使之能够完成图书建立，借书和归还的功能，并能够按照样例输入和输出。 #include <iostream> using namespace std; class Book { char bookname[40]; double price; int number; public: Book::Book(char *name="", double pri=0, int num=0) { //构造函数，将这部分补充完整 } void set(char *name, double pri, int num) { strcpy(bookname, name); price=pri; number=num; } void borrow(); void restore(); void display(); }; void Book::borrow() { if (number==0 ) { cout << "已没存书，退出！" << endl; } number = number - 1; cout << "借一次，现存书量为：" << number << endl; } void Book::restore() { number = number + 1; cout << "还一次，现存书量为：" << number << endl; } void Book::display() { cout << "存书情况：" << endl << "bookname:" << bookname << endl << "price:" << price << endl << "number:" << number << endl; } int main() { Book computer; char bookname[40]; double price; int number; cin>>bookname>>price>>number; computer.set(bookname,price,number); cin>>bookname>>price>>number; Book math(bookname,price,number); computer.borrow(); computer.borrow(); computer.restore(); math.restore(); math.borrow(); math.borrow(); computer.display(); math.display(); }

下面是完整的程序：

#include <iostream>
#include <cstring>   //需要引入cstring库

using namespace std;

class Book {
    char bookname[40];
    double price;
    int number;

public:
    Book(char *name="", double pri=0, int num=0) {
        strcpy(bookname, name);
        price = pri;
        number = num;
    }
    void set(char *name, double pri, int num) {
        strcpy(bookname, name);
        price = pri;
        number = num;
    }
    void borrow();
    void restore();
    void display();
};

void Book::borrow() {
    if (number == 0) {
        cout << "已没存书，退出！" << endl;
        return;
    }
    number = number - 1;
    cout << "借一次，现存书量为：" << number << endl;
}

void Book::restore() {
    number = number + 1;
    cout << "还一次，现存书量为：" << number << endl;
}

void Book::display() {
    cout << "存书情况：" << endl 
         << "bookname:" << bookname << endl 
         << "price:" << price << endl 
         << "number:" << number << endl;
}

int main() {
    Book computer;
    char bookname[40];
    double price;
    int number;

    cin >> bookname >> price >> number;
    computer.set(bookname, price, number);

    cin >> bookname >> price >> number;
    Book math(bookname, price, number);

    computer.borrow();
    computer.borrow();
    computer.restore();
    math.restore();
    math.borrow();
    math.borrow();
    computer.display();
    math.display();

    return 0;
}

下面是样例输入和输出：

**输入：**

Computer 55.6 10
Math 30.7 20

**输出：**

借一次，现存书量为：9
借一次，现存书量为：8
还一次，现存书量为：9
还一次，现存书量为：21
借一次，现存书量为：19
借一次，现存书量为：18
存书情况：
bookname:Computer
price:55.6
number:9
存书情况：
bookname:Math
price:30.7
number:18