#include <iostream>

using namespace std;

class String {

public:

    //    构造函数

    String(const char *str=NULL);

    //    拷贝构造函数

    String(const String& other);

    //    赋值函数

    String& operator =(const String &other);

    //    析构函数

    ~String(void);

private:

    char *data;

};

String::String(const char * str) {

    if (str == NULL)

    {

        data = new char[];

        *data = '\0';

    }

    else {

        int len = strlen(str) + ;

        data = new char[len];

        strcpy(data, str);

    }

}

String::String(const String& other) {

    int len = strlen(other.data) + ;

    data = new char[len];

    strcpy(data, other.data);

}

String & String::operator=(const String& other) {

    //    判断是不是自赋值

    if (this == &other)

        return *this;

    delete[]data;

    int len = strlen(other.data) + ;

    data = new char[len];

    strcpy(data, other.data);

    //    返回本对象的引用

    return *this;

}

String::~String() {

    delete[]data;

}