[C++] String 코딩하기

String을 사용하지 않고 String역할을 하는 함수(Mystring) 코딩하기

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstring>
//#include<string>
 
using namespace std;
 
class Mystring
{
    char *a;
    int len;
public:
    Mystring() {
        this->a = new char;
    }
 
    //Mystring one("lottery winner!");
    Mystring(const char *a) {
        len = strlen(a);
        this->a = new char[len + 1];
        strcpy(this->a, a);
    }
 
    // Mystring two(20, '$');
    Mystring(int len, const char a) {
        this->len = len;
        this->a = new char[this->len + 1];
        for (int i = 0; i < len; i++) {
            this->a[i] = a;
        }
        this->a[len] = NULL;
    }
    ~Mystring() { delete[]a; } //소멸자
 
    // Mystring three(one); 
    Mystring(Mystring &a) {
        this->len = a.len;
        this->a = new char[this->len + 1];
        strcpy(this->a, a.a);
    }
    Mystring(char *a, int num) {//8번
        this->a = new char[num+1];
 
        strncpy(this->a, a, num);
        
        this->a[num] = NULL;
    }
    Mystring(char *a, char *b) {//9번
        len = strlen(a) - strlen(b);
 
        this->a = new char[len + 1];
        strncpy(this->a, a, len);
 
        this->a[len] = NULL;
    }
 
    // one += "oops";
    Mystring& operator +=(const char *a) {
        int len2 = strlen(a);// oops 길이
        char *    str = new char[len + 1]; //char 타입 메모리 동적할당
 
        strcpy(str, this->a); //str에 lottery winner! 복사
 
        delete[]this->a; //원래 있던 this->a 해제
        this->a = new char[len + len2 + 1]; // this->a 새로 할당
 
        strcat(str, a); // str(lottery winner!) + oops
        strcpy(this->a, str); // this->a에 str(lottery winner!oops) 복사
 
        return *this; //this->a 리턴
    }
 
    //two = "sorry!that was";
    Mystring& operator =(const Mystring &a) {
        len = strlen(a.a);
        this->a = new char[len + 1];
        strcpy(this->a, a.a);
 
        return *this;
    }
 
    // three[0]='p' pottery winner!
    char& operator [](int a) {
        return this->a[a];
    }
 
    
    // four = two + three;
    Mystring& operator +(const Mystring &a) {
        int len2 = strlen(a.a);
        char *str = new char[len + 1];
        //a.a = pottery winner!
        strcpy(str, this->a);
 
        //delete[]this->a; 
        this->a = new char[len + len2 + 1];
 
        strcpy(this->a, str);
        strcat(this->a, a.a);
 
        return *this;
    }
 
    friend ostream& operator << (ostream &a, Mystring &aa);
    friend istream& operator >>(istream &in, Mystring &aa);
};
 
// 출력
ostream& operator << (ostream &out, Mystring &aa) {
    out << aa.a;
    return out;
}
 
// 입력
istream& operator >>(istream &in, Mystring &aa) {
    char str[100];
    in >> str;
 
    Mystring a(str);
 
    aa = a;
 
    return in;
}
int main()
{
    Mystring one("lottery winner!");//생성자함수호출
    cout << one << endl;  //출력연산자함수호출
 
    Mystring two(20, '$');//생성자함수호출
    cout << two << endl;//출력연산자함수호출
 
    Mystring three(one); // 복사생성자호출
    cout << three << endl; //출력연산자함수호출
 
    one += "oops"; // +=연산자함수호출 ( strcat함수 
    cout << one << endl;//문자열결합 
 
    two = "sorry!that was";//대입연산자함수 호출 
    cout << two << endl;
 
    three[0] = 'p';//[]첨자연산자함수 호출 
    cout << three << endl;
 
    Mystring four;
    four = two + three;
    cout << four << endl;
 
    char alls[] = "all's well that ends well";
    Mystring five(alls, 20); //생성자호출
    cout << five << "!\n";
 
    Mystring six(alls + 6, alls + 10);  //생성자
    cout << six << ",";
 
    Mystring seven(&five[6], &five[10]);  //생성자
    cout << seven << "...\n";
 
    Mystring eight;
    cout << "문자열 입력하세요 :";
    cin >> eight;  // >>연산자호출
    cout << " 입력한 문자열은 \"" << eight << "\" 입니다 " << endl;
}