完成下列的 String 类，并在主函数 main( )中测试它。 class String { public: String(const char *str = NULL); // constructor String(const String &other); // copy constructor ~ String(void); // destructor String & operate =(char *str); String & operate =(const String &other);// 重载=运算符 int operator==(String &other); // 重载==运算符 int operator==(char *str); private: char *m_data; // used for storing the string int length; };

以下是 String 类的实现以及在主函数 main() 中的测试。

#include <iostream>
#include <cstring>

using namespace std;

class String {
public:
    String(const char *str = NULL);
    String(const String& other);
    ~String(void);
    String& operator=(char *str);
    String& operator=(const String& other);
    int operator==(String& other);
    int operator==(char *str);
private:
    char *m_data;
    int length;
};

String::String(const char* str) {
    if (str != NULL) {
        length = strlen(str);
        m_data = new char[length + 1];
        strcpy(m_data, str);
    }
    else {
        length = 0;
        m_data = new char[1];
        *m_data = '\0';
    }
}

String::String(const String& other) {
    length = other.length;
    m_data = new char[length + 1];
    strcpy(m_data, other.m_data);
}

String::~String(void) {
    delete[] m_data;
}

String& String::operator=(char *str) {
    if (m_data == str) {
        return *this;
    }
    if (str != NULL) {
        length = strlen(str);
        char *temp = new char[length + 1];
        strcpy(temp, str);
        delete[] m_data;
        m_data = temp;
    }
    else {
        length = 0;
        delete[] m_data;
        m_data = new char[1];
        *m_data = '\0';
    }
    return *this;
}

String& String::operator=(const String& other) {
    if (m_data == other.m_data) {
        return *this;
    }
    length = other.length;
    char *temp = new char[length + 1];
    strcpy(temp, other.m_data);
    delete[] m_data;
    m_data = temp;
    return *this;
}

int String::operator==(String& other) {
    return strcmp(m_data, other.m_data) == 0;
}

int String::operator==(char *str) {
    return strcmp(m_data, str) == 0;
}

int main() {
    String s1("hello");
    String s2(s1);
    String s3("world");
    String s4;
    s4 = s1;

    cout << s1.operator==("hello") << endl; // 1
    cout << s1.operator==(s2) << endl; // 1
    cout << s1.operator==(s3) << endl; // 0
    cout << s1.operator==(s4) << endl; // 1

    return 0;
}