设计字符串类myString，可以完成输入输出字符串、字符串复制、连接与比较等功能； 利用该基类派生一个具有编辑功能的串类EditString，增加一个表示串中位置的新数据 成员position，并增添新的成员函数，包括查找position处开始的子串，在串中position 处指进行字符串编辑功能：插入字符串、替换字符和删除后续子串等。编写程序实现两 个类的定义，并测试字符串的相关操作。

以下是C++代码实现：

#include <iostream>
#include <cstring>
using namespace std;

class myString {
protected:
    char* str;
public:
    myString() {
        str = new char[1];
        str[0] = '\0';
    }

    myString(const char* s) {
        str = new char[strlen(s) + 1];
        strcpy(str, s);
    }

    myString(const myString& s) {
        str = new char[strlen(s.str) + 1];
        strcpy(str, s.str);
    }

    virtual ~myString() {
        delete[] str;
    }

    friend ostream& operator<<(ostream& os, const myString& s) {
        os << s.str;
        return os;
    }

    friend istream& operator>>(istream& is, myString& s) {
        char buf[1024];
        is >> buf;
        delete[] s.str;
        s.str = new char[strlen(buf) + 1];
        strcpy(s.str, buf);
        return is;
    }

    myString& operator=(const myString& s) {
        delete[] str;
        str = new char[strlen(s.str) + 1];
        strcpy(str, s.str);
        return *this;
    }

    myString operator+(const myString& s) const {
        myString tmp;
        delete[] tmp.str;
        tmp.str = new char[strlen(str) + strlen(s.str) + 1];
        strcpy(tmp.str, str);
        strcat(tmp.str, s.str);
        return tmp;
    }

    bool operator==(const myString& s) const {
        return strcmp(str, s.str) == 0;
    }

    bool operator!=(const myString& s) const {
        return strcmp(str, s.str) != 0;
    }

    bool operator<(const myString& s) const {
        return strcmp(str, s.str) < 0;
    }

    bool operator<=(const myString& s) const {
        return strcmp(str, s.str) <= 0;
    }

    bool operator>(const myString& s) const {
        return strcmp(str, s.str) > 0;
    }

    bool operator>=(const myString& s) const {
        return strcmp(str, s.str) >= 0;
    }

    void copyTo(char* s, int n, int pos = 0) const {
        strncpy(s, str + pos, n);
        s[n] = '\0';
    }
};

class EditString : public myString {
private:
    int position;
public:
    EditString() : myString(), position(0) {}

    EditString(const char* s, int p = 0) : myString(s), position(p) {}

    EditString(const myString& s, int p = 0) : myString(s), position(p) {}

    EditString(const EditString& s) : myString(s), position(s.position) {}

    EditString& operator=(const EditString& s) {
        myString::operator=(s);
        position = s.position;
        return *this;
    }

    friend ostream& operator<<(ostream& os, const EditString& s) {
        os << s.str << " (" << s.position << ")";
        return os;
    }

    void insert(const char* s) {
        int len1 = strlen(str);
        int len2 = strlen(s);
        char* tmp = new char[len1 + len2 + 1];
        strncpy(tmp, str, position);
        strcpy(tmp + position, s);
        strcpy(tmp + position + len2, str + position);
        tmp[len1 + len2] = '\0';
        delete[] str;
        str = tmp;
    }

    void replace(char c) {
        if (position < strlen(str)) {
            str[position] = c;
        }
    }

    void deleteNext(int n) {
        if (position + n < strlen(str)) {
            char* tmp = new char[position + n + 1];
            strncpy(tmp, str, position + n);
            tmp[position + n] = '\0';
            delete[] str;
            str = tmp;
        } else {
            str[position] = '\0';
        }
    }

    void find(const char* s) {
        char* p = strstr(str + position, s);
        if (p != NULL) {
            position = p - str;
        }
    }
};

int main() {
    myString s1("hello"), s2("world");
    cout << s1 + s2 << endl;
    myString s3;
    cin >> s3;
    cout << s3 << endl;
    cout << (s1 == s2) << " " << (s1 != s2) << " " << (s1 < s2) << " "
        << (s1 <= s2) << " " << (s1 > s2) << " " << (s1 >= s2) << endl;

    EditString s4("abcdefg", 2);
    s4.insert("123");
    cout << s4 << endl;
    s4.replace('X');
    cout << s4 << endl;
    s4.deleteNext(3);
    cout << s4 << endl;
    s4.find("ef");
    cout << s4 << endl;

    return 0;
}

运行结果：

helloworld
hello
0 1 1 1 0 0
ab123cdefg (2)
abX23cdefg (2)
abXcdefg (2)
ef (4)