String类

class string

{

public:

                string( const char *str);

                string( const string &other);

                ~string();

                 string &operator=(const string &other);

private:

                 char *data;

};

//构造函数

string::string(const char *str)

                 if (str == null)   //指针可能为空，要判断

                {

                                data = new char [1];

                                *data = '\0';

                }

                 else

                                 int length = strlen(str );

                                data = new char [length + 1];

                                strcpy(data, str);

}

//析构函数

string::~string()

                 delete data;

//拷贝构造函数

string::string(const string & other)

                 int length = strlen(other .data);

                data = new char [length + 1];

                strcpy(data, other.data);

//赋值函数

string &string ::operator=(const string & other)

                 if (this == &other)   //引用不可能为空，所以不用判断,注意不要错写为：if(*this==other)

                                 return *this ;

                 delete data; //释放原有的内存资源，以后没机会释放

                 int length = strlen(other .data);   //strlen不包含‘0’，strcpy包含‘0’一起复制

                 return *this ;  //返回本对象的引用，为了实现像a=b=c这样的链式表达

时间问题，后期有需要补充的会陆续补充