仿照string类，自己手动实现 My_string

list.h

#ifndef LIST_H
#define LIST_H
#include <iostream>using namespace std;class My_string
{
private:char *ptr;int size;int len;public://无参构造My_string();//有参构造My_string(const char * src);My_string(int num, char value);//拷贝构造My_string(const My_string& other);//拷贝赋值My_string & operator= (const My_string &other);//析构构造~My_string();//判空bool MYempty() const;//尾插void push_back(char value);//尾删void pop_back();//at函数实现char &at(int index);//清空函数void clear();//返回C风格字符串char *data();//返回实际长度int get_length();//返回当前最大容量int get_size();//君子函数：二倍扩容void resize();void show();
};
#endif // LIST_H

list.c

#include "list.h"
using namespace std;
My_string::My_string():size(15)
{this->ptr = new char[15];this->ptr[0] = '\0';this->len = 0;
}
//有参构造
My_string::My_string(const char * src)
{this->len = 0;for(int i=0;src[i] != 0;i++){this->len++;}this->size = this->len+1;this->ptr = new char[this->size];for(int i = 0;src[i] != 0;i++){this->ptr[i] = src[i];}
}
My_string::My_string(int num, char value)
{this->len = num;this->size = this->len+1;this->ptr = new char[this->size];for (int i = 0; i < this->len; i++){this->ptr[i] = value; // 用value填充数组}this->ptr[this->len] = '\0'; // 添加结束符
}
//拷贝构造
My_string::My_string(const My_string& other):ptr(new char[other.len + 1]),size(other.size), len(other.len)
{for(int i = 0;other.ptr[i] != 0;i++) // 复制字符串内容{this->ptr[i] = other.ptr[i];}
}
//拷贝赋值
My_string & My_string::operator= (const My_string &other)
{if(this != &other)               //防止自己给自己赋值{this->size = other.size;this->len = other.len;//this->ptr = other.ptr;                 //浅拷贝for(int i = 0;other.ptr[i] != 0;i++)     //深拷贝{this->ptr[i] = other.ptr[i];}}return *this;                  //返回值自身的引用
}
//析构构造
My_string::~My_string()
{delete[] ptr;     //需要显性定义析构函数，在析构函数的函数体内释放堆区空间cout<<"Person::析构函数，this = "<<this<<endl;
}
//判空
bool My_string::MYempty() const
{return this->ptr == nullptr || this->len == 0; // 如果指针为空或长度为0，则认为是空
}
//尾插
void My_string::push_back(char value)
{this->size++;this->ptr[len] = value;this->len++;this->ptr[size] = 0;
}
//尾删
void My_string::pop_back()
{this->ptr[len-1] = 0;this->size--;this->len--;
}
//at函数实现
char & My_string::at(int index)
{static char num;num = this->ptr[index-1];return num;  
}
//清空函数
void My_string::clear()
{this->size = 15;delete[] ptr;this->ptr = new char[1];this->ptr[0] = '\0';this->len = 0;
}
//返回C风格字符串
char *My_string::data()
{return ptr;
}
//返回实际长度
int My_string::get_length()
{return this->len;
}
//返回当前最大容量
int My_string::get_size()
{return this->size;
}
//君子函数：二倍扩容
void My_string::resize()
{size *= 2; // 容量翻倍char* newptr = new char[size]; // 分配新的内存for(int i = 0;this->ptr[i] != 0;i++)     //深拷贝{newptr[i] = this->ptr[i];}delete[] ptr; // 释放旧内存this->ptr = newptr; // 更新指针
}
void My_string::show()
{cout<< "ptr = " << this->ptr << endl;cout<< "size = " << this->size << endl;cout<< "len = " << this->len << endl;
}

main.c

#include "list.h"using namespace std;int main()
{My_string s;s.show();if(s.MYempty()==1){cout << "s" << "为空" << endl;}My_string s1("hello world");s1.show();My_string s2(5,'A');s2.show();My_string s3(s1);s3.show();s.operator=(s2);s.show();My_string s4 = s1;s4.push_back('B');s4.show();s4.pop_back();s4.show();cout << s4.at(3) << endl;s4.clear();if(s4.MYempty()==1){cout << "s4" << "为空" << endl;}s3.data();s3.show();cout << s2.get_length() << endl;cout << s2.get_size() << endl;s1.resize();s1.show();return 0;
}