c++ — 运算符重载与strcmp自实现

#include <iostream>
#include <string.h>
#include <stdlib.h>

using namespace std;

class myStrcmp
{
public:
    //在声明处默认参数
    myStrcmp(char *str=NULL);
    //析构器
    ~myStrcmp()
    {
        cout<<"caibi"<<endl;
        delete []str;
    }
    //运算符重载
    int operator > (myStrcmp &str2);
    int operator < (myStrcmp &str2);
    int operator = (myStrcmp &str2);
private:
    char *str;   //成员函数str存放字符串
};

//构造器
myStrcmp::myStrcmp(char *str)
{
    //如果没有值传进来，字符串置空
    if(str==NULL)
    {
        this->str =new char[1];
        *this->str='\0';
    }
    //如果有值传入，使用strcpy拷贝进对象的str中
    else
    {
        this->str =new char[strlen(str)+1]; //申请空间
        strcpy(this->str,str);
    }
}

//strcmp运算符重载与自实现
int myStrcmp::operator > (myStrcmp &str2)
{
    //字符比较，不等退出
    char *p=str2.str;    //临时指针变量p，合理调用析构器析构str2
    for(;*this->str == *p && *p!= '\0' && *this->str != '\0';(this->str)++,p++);

    //比较退出时第一个字符大小
    if(*this->str > *p)
    return 1;
}

int myStrcmp::operator < (myStrcmp &str2)
{
    //字符比较，不等退出
    char *p=str2.str;     //临时指针变量p
    for(;*this->str == *p && *p != '\0' && *this->str != '\0';(this->str)++,p++);

    //比较退出时第一个字符大小
    if(*this->str < *p)
    return -1;
}

int myStrcmp::operator = (myStrcmp &str2)
{

    //字符比较，不等退出
    char *p=str2.str;   //临时指针变量p
    for(;*this->str == *p && *p != '\0' && *this->str != '\0';(this->str)++,p++);

    //比较退出时第一个字符大小
    if((*this->str) == (*p))
    return 0;
}

int main()
{
    myStrcmp str1("panda");  //字符串s1
    myStrcmp str2("panmsa");  //字符串s2

    //判断str1与str2大小
    if(str1>str2==1)
        cout<<"str1>str2"<<endl;
    else if(str1<str2==-1)
        cout<<"str1<str2"<<endl;
    else if((str1=str2)==0)
        cout<<"str1=str2"<<endl;

	system("pause");
    return 0;
}

　　总结：析构器在析构时，若未定义str2的临时指针变量，str2会析构错误；不要改变指针位置，使用下标进行比较

#include <iostream>
#include <string.h>
#include <stdlib.h>

using namespace std;

class myStrcmp
{
public:
    //在声明处默认参数
    myStrcmp(char *str=NULL);
    //析构器
    ~myStrcmp()
    {
        cout<<"caibi"<<endl;
        delete []str;
    }
    //运算符重载
    int operator > (myStrcmp &str2);
    int operator < (myStrcmp &str2);
    int operator = (myStrcmp &str2);
private:
    char *str;   //成员函数str存放字符串
};

//构造器
myStrcmp::myStrcmp(char *str)
{
    //如果没有值传进来，字符串置空
    if(str==NULL)
    {
        this->str =new char[1];
        *this->str='\0';
    }
    //如果有值传入，使用strcpy拷贝进对象的str中
    else
    {
        this->str =new char[strlen(str)+1]; //申请空间
        strcpy(this->str,str);
    }
}

//strcmp运算符重载与自实现
int myStrcmp::operator > (myStrcmp &str2)
{
    //字符比较，不等退出
    int i=0;
	for(;this->str[i] == str2.str[i] && str2.str[i]!= '\0' && this->str[i] != '\0';i++);

    //比较退出时第一个字符大小
    if(this->str[i] > str2.str[i])
    return 1;
}

int myStrcmp::operator < (myStrcmp &str2)
{
  //字符比较，不等退出
    int i=0;
	for(;this->str[i] == str2.str[i] && str2.str[i]!= '\0' && this->str[i] != '\0';i++);

    //比较退出时第一个字符大小
    if(this->str[i] < str2.str[i])
    return -1;
}

int myStrcmp::operator = (myStrcmp &str2)
{

    //字符比较，不等退出
    int i=0;
	for(;this->str[i] == str2.str[i] && str2.str[i]!= '\0' && this->str[i] != '\0';i++);

    //比较退出时第一个字符大小
    if((this->str[i]) == (str2.str[i]))
    return 0;
}

int main()
{
    myStrcmp str1("panda");  //字符串s1
    myStrcmp str2("pandaa");  //字符串s2

    //判断str1与str2大小
    if(str1>str2==1)
        cout<<"str1>str2"<<endl;
    else if(str1<str2==-1)
        cout<<"str1<str2"<<endl;
    else if((str1=str2)==0)
        cout<<"str1=str2"<<endl;

	system("pause");
    return 0;
}