思维导图

 仿照string类，实现myString类

/* 
   ---------------------------------
    @author：YoungZorn
    created on 2023/7/19 19:20.
   ---------------------------------
*/
#include<iostream>
#include<cstring>

using namespace std;

class myString
{
private:
    char *str;           //记录c风格的字符串
    int size;            //记录字符串的实际长度
public:
    //无参构造
    myString():size(10)
    {
        str = new char[size];         //构造出一个长度为10的字符串
        strcpy(str,"");         //初始化myString对象str为空串
    }
    //有参构造
    myString(const char *s)          //string  s("hello world")
    {
        size = strlen(s);
        str = new char[size+1];   //末尾添加 '\0'
        strcpy(str, s);   //--->str = "hello world"
    }

    //拷贝构造
    myString(const myString & other):str(new char(*other.str)),size(other.size){}

    //析构函数
    ~myString(){delete [] str;}

    //拷贝赋值函数
    myString& operator=(const myString& other){
        if(this != &other){
            delete [] str;  //释放原有的内存
            this->size = other.size;
            this->str = new char(*(other.str));
        }
        return *this;
    }

    //判空函数
    bool isEmpty(){
        if(strcmp(str,"") == 0){
            return true;
        }
        return false;
    }

    //size函数
    int strSize(){
        if (isEmpty()){
            return -1;
        }
        return strlen(str);
    }

    //c_str函数
    const char *str_c_str()const{
        return str;   //返回一个C风格的字符串
    }

    //at函数
    char &at(int pos){
        if (isEmpty()){
            const int &ref = -1;
            return (char &)ref;
        }
        return str[pos];   //返回字符所在字符串的下标
    }

    //加号运算符重载  (+)
    const myString operator+ (const myString & R) const{
        int newSize = size + R.size;  //新字符串的长度
        char *newStr = new char[newSize+1];  //分配新字符串内存
        strcpy(newStr, this->str);
        strcat(newStr,R.str);
        return myString(newStr);
    }

    //加等于运算符重载 (+=)
    const myString operator+= (const myString & R){
        size += R.size;  //更新size
        strcat(this->str,R.str);  //将R.str追加到str上
        return myString(this->str);
    }

    //关系运算符重载 (>)
    bool operator> (const myString & R) const {
        int flag = strcmp(this->str,R.str);
        if (flag > 0)
            return true;
        return false;
    }
};

int main(){
    myString string1 = "hello";
    bool flag = string1.isEmpty();
    cout<<flag<<endl;

    cout<<string1.strSize()<<endl;

    cout<<"at[0]:"<<string1.at(0)<<endl;

    myString s1 = "qwe";
    myString s2 = "asd";

    cout<<(s1>s2)<<endl; //判断 s1 和 s2 的大小

    s1 += s2;
    cout<<"s1 += s2 = "<<s1.str_c_str()<<endl;  // +=
    cout<<s1.str_c_str()<<endl;

    myString s3 = "aaa";
    myString s4 = "bbb";

    myString s5 = s3 + s4;
    cout<<"s3 + s4 = "<<s5.str_c_str()<< endl;  // +

    return 0;
}