0,精通Python,62.37==>1 1,精通C++,49.21==>1 1,精通C++,49.21==>1 訪問索引超過范圍Hit any key to continue... #include <iostream> #include <cstring> #include <vector> using namespace std;class Book { private:int _id;char* _name;float _price;static inline int nowid{0};int _bookCount{1}; public : Book(int id, char* name, float price): _id(id), _price(price){int nameLen = strlen(name);_name = new char[nameLen + 1];strcpy(_name, name);}Book(char* name, float price):Book(nowid,name,price){nowid++;}~Book(){delete[] _name;}friend const Book& operator +(const Book& leftBook,const Book& rightBook){if (leftBook==rightBook) {Book *book=new Book(rightBook._name, rightBook._price); book->_bookCount=leftBook._bookCount+rightBook._bookCount;return *book;}else{return leftBook;}}friend const Book& operator -(const Book& leftBook,const Book& rightBook){if (leftBook==rightBook) {Book *book=new Book(rightBook._name, rightBook._price); book->_bookCount=leftBook._bookCount-rightBook._bookCount;if ( book->_bookCount<0) book->_bookCount=0;return *book;}else{return leftBook;} } Book& operator -=(const Book& otherBook){if (*this==otherBook) {_bookCount-=otherBook._bookCount;if ( _bookCount<0) _bookCount=0;return *this;}else{return *this;} } Book& operator +=(const Book& otherBook){if (*this==otherBook) {_bookCount+=otherBook._bookCount;return *this;}else{return *this;} } friend const bool operator ==(const Book& leftBook,const Book& rightBook){if (strcmp (rightBook._name,leftBook._name) == 0 && rightBook._price==leftBook._price) {return true;}else{return false;} } friend const bool operator !=(const Book& leftBook,const Book& rightBook){if (strcmp (rightBook._name,leftBook._name) == 0 && rightBook._price==leftBook._price) {return false;}else{return true;} } const void print() const{cout<<_id<<","<<_name<<","<<_price<<"==>"<< _bookCount<<endl;}void printCount(){cout<<_name<<":"<<_price<<"==>"<< _bookCount<<endl; } }; class BookS{ private:vector<Book*> _myBooks; public:void addBook(Book* book){_myBooks.push_back(book); }void print() {for(const Book *bk:_myBooks){bk->print();}}Book& operator[](int i){ return *(_myBooks.at(i));}};int main(int argc, char **argv) {Book *book1=new Book("精通Python",62.37); Book *book2=new Book("精通C++",49.21); BookS myBks;myBks.addBook(book1); myBks.addBook(book2); myBks.print();try{ myBks[1].print();myBks[2].print(); }catch(std::out_of_range e){cout<<"訪問索引超過范圍"<<endl;}}

下面對[]的重載，對vector使用.at的方式訪問，這樣可以拋出超范圍異常，如果直接使用[]將導致超過范圍

Book& operator[](int i){ return *(_myBooks.at(i));}

總結

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