#include <iostream>

#include <string.h>

#include <stdlib.h>

using namespace std;

class String

{

    public:

        String (const char *str=NULL); //普通构造函数

        String (const String &other);  //复制构造函数

        ~String (void); //析构函数

        String &operator=(const String &other); //赋值函数

        friend ostream &operator<<(ostream &output, const String &other); //输出函数

    private:

        char *data; //保存字符串

};

//普通构造函数

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);

    }

}

//复制构造函数

String::String(const String &other)

{

    int len = strlen(other.data);

    data = new char[len+];

    strcpy(data, other.data);

}

//析构函数

String::~String()

{

    delete[] data;

}

//赋值函数

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

{

    if (this == &other)

    {

        return *this;

    }

    delete[] data;

    int len = strlen(other.data);

    data = new char[len+];

    strcpy(data, other.data);

    return *this;

}

//输出函数

ostream &operator<<(ostream &output, const String &other)

{

    output<<other.data;

    return output;

}

int main()

{

    String s1("hello");

    cout << s1 << endl;

    String s2=s1;

    cout << s2 << endl;

    String s3;

    s3=s1;

    cout << s3 << endl;

}