[C++] string类的实现

Dear 丶 2022-02-03 18:45 260阅读 0赞

string 类的实现是一个经常考的面试题，主要考察运算符的重载以及内存管理，还有可以考察面试者的代码风格。这是我自己实现的一个简单的 string 类，有需要的可以参考。代码如下：

##### 1、mystring.h #####

// 自定义 MyString 类
    #define _CRT_SECURE_NO_WARNINGS
    #pragma once
    #include <iostream>
    
    using namespace std;
    
    class MyString
    { 
    public:
    	MyString(const char* c_str = NULL);
    	~MyString() {  delete[] m_data; this->m_data = NULL; };
    
    	// 拷贝构造函数
    	MyString(const MyString& str);
    
    	// 拷贝复制函数
    	MyString& operator=(const MyString& str);
    
    	// <<, >>
    	friend ostream& operator<<(ostream& out, const MyString& str);
    	friend istream& operator>>(istream& in, MyString& str);
    
    	// +
    	MyString operator+(const MyString& str);
    
    	// ==
    	bool operator==(const MyString& str);
    
    	// []
    	char operator[](int n);
    
    	// 字符串长度
    	int length() const {  return strlen(this->m_data); }
    
    	// 获取 C 风格字符串
    	char* get_c_str() const {  return this->m_data; }
    
    private:
    	char* m_data;
    };

##### 2、mystring.cpp #####

#include "mystring.h"
    
    MyString::MyString(const char * c_str):m_data(NULL)
    { 
    	if (c_str)
    	{ 
    		m_data = new char[strlen(c_str) + 1];
    		strcpy(this->m_data, c_str);
    	}
    	else
    	{ 
    		m_data = new char[1];
    		*m_data = '/0';
    	}
    }
    
    MyString::MyString(const MyString & str)
    { 
    	m_data = new char[strlen(str.m_data) + 1];
    	strcpy(this->m_data, str.m_data);
    }
    
    MyString & MyString::operator=(const MyString & str)
    { 
    	if (this == &str)
    	{ 
    		return *this;
    	}
    
    	delete[] m_data;
    	m_data = new char[strlen(str.m_data) + 1];
    	strcpy(this->m_data, str.m_data);
    
    	return *this;
    }
    
    MyString MyString::operator+(const MyString & str)
    { 
    	MyString* new_string = new MyString;
    	if (str.m_data == NULL)
    	{ 
    		*new_string = *this;
    	}
    	else if (this->m_data == NULL)
    	{ 
    		*new_string = str;
    	}
    	else
    	{ 
    		new_string->m_data = new char[strlen(this->m_data) + strlen(str.m_data) + 1];
    		strcpy(new_string->m_data, this->m_data);
    		strcat(new_string->m_data, str.m_data);
    	}
    	
    	return *new_string;
    	delete new_string;
    }
    
    bool MyString::operator==(const MyString & str)
    { 
    	if (this->length() != str.length())
    		return false;
    	return strcmp(this->m_data, str.m_data) ? false : true;
    }
    
    char MyString::operator[](int n)
    { 
    	if (n < 0 || n >= this->length())
    	{ 
    		cout << "argument error!" << endl;
    		return NULL;
    	}
    	else
    	{ 
    		return this->m_data[n];
    	}
    }
    
    ostream& operator<<(ostream& out, const MyString& str)
    { 
    	out << str.get_c_str();
    	return out;
    }
    
    istream& operator>>(istream& in, MyString& str)
    { 
    	char tmp[255] = {  0 };
    	in >> tmp;
    	str.m_data = new char[strlen(tmp) + 1];
    	strcpy(str.m_data, tmp);
    	return in;
    }

##### 3、测试函数 #####

// 2. 字符串类测试函数
    void mystring_test()
    { 
    	MyString str1("hello");
    	MyString str2(str1);
    	MyString str3 = ", world";
    	MyString str4 = str1 + str3;
    
    	cout << "str1: " << str1 << ", " << "str2: " << str2 << endl;
    	cout << str2.length() << endl;
    	cout << str2.get_c_str() << endl;
    	cout << "str3: " << str3 << endl;
    	cout << "str4: " << str4 << endl;
    	cout << str4[1] << endl;
    	
    }

**运行结果：**

str1: hello, str2: hello
    5
    hello
    str3: , world
    str4: hello, world
    e
    请按任意键继续. . .