【复制构造、重载等】MyString

#include <iostream>
#include <string>
#include <cstring>
using namespace std;
class MyString
{
    char *p;
public:
    MyString(const char *s)
    {
        if (s)
        {
            p = new char[strlen(s) + 1];
            strcpy(p, s);
        }
        else
            p = NULL;
    }
    ~MyString()
    {
        if (p)
            delete[] p;
    }
    MyString(const MyString &s)
    {
        if (s.p)
        {
            p = new char[strlen(s.p) + 1];
            strcpy(p, s.p);
        }
        else
            p = NULL;
    }
    MyString &operator=(const MyString s)
    {
        if (p)
            delete[] p;
        if (s.p)
        {
            p = new char[strlen(s.p) + 1];
            strcpy(p, s.p);
        }
        else
            p = NULL;
        return *this;
    }
    void Copy(const char *s)
    {
        if (p)
            delete[] p;
        if (s)
        {
            p = new char[strlen(s) + 1];
            strcpy(p, s);
        }
        else
            p = NULL;
    }
    friend ostream &operator<<(ostream &o, const MyString s)
    {
        o << s.p;
        return o;
    }
};
int main()
{
    char w1[200], w2[200];
    while (cin >> w1 >> w2)
    {
        MyString s1(w1), s2 = s1;
        MyString s3(NULL);
        s3.Copy(w1);
        cout << s1 << "," << s2 << "," << s3 << endl;
        s2 = w2;
        s3 = s2;
        s1 = s3;
        cout << s1 << "," << s2 << "," << s3 << endl;
    }
}

• 这个题要搞复制构造函数、重载“=”“<<”运算符，需要用到深拷贝
• 即使是friend函数也可以在类内实现