剑指offer 赋值运算符

• 把传入参数设为引用，就可以不调用拷贝构造函数，少了一次拷贝节省了内存，返回值是该类的引用，这样才能连续赋值。

• 引用，防止产生一次拷贝副本。

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

using namespace std;

class CMystring
{
public:
    CMystring(const char* pData = NULL);
    CMystring(const CMystring &str );
    ~CMystring();
    CMystring &operator=(const CMystring &str);

    void print();

private:
    char *m_pdata;
};




CMystring::CMystring(const char* pdata) {
    if (pdata==NULL)
    {
        m_pdata = new char[1];
        m_pdata[0] = '\0';
    }
    else
    {
        
        m_pdata = new char[strlen(pdata) + 1];
        strcpy(m_pdata, pdata);
    }
}
CMystring::CMystring(const CMystring &str)
{
    int lenth = strlen(str.m_pdata);
    m_pdata = new char[lenth + 1];
    strcpy(m_pdata, str.m_pdata);
}
CMystring::~CMystring()
{
    delete[] m_pdata;
}

CMystring& CMystring::operator=(const CMystring &str) {
    if (this==&str)
        return *this;

    delete[]m_pdata;
    m_pdata = NULL;

    m_pdata = new char[strlen(str.m_pdata) + 1];
    strcpy(m_pdata, str.m_pdata);
    return *this;
      /*
        CMyString temp(str);
        char *ptemp = temp.m_pdata;
        temp.m_pdata=m_pdata;
        m_pdata=ptemp;
        */

}
void CMystring::print() {
    printf("%s", m_pdata);
}
void Test1() {

    printf("Test1 begin:\n");
    char* text = "hello world";
    CMystring str1(text);
    CMystring str2;
    str2 = str1;
    printf("The expected string is %s\n:", text);
//  str1.print();
    printf("The actually result is:");
    str2.print();
    printf("\n");
}

/************************************************************************/
/* 自己复制test                                                                     */
/************************************************************************/
void Test2() {
    printf("Test2 begin:\n");
    char *text = "Hello World2";

    CMystring  str2(text);
    printf("The expected string is: %s\n", text);
    printf("The actually result is:");
    str2 = str2;
    str2.print();
    printf("\n");
}

/* 连续复制 */
void Test3() {
    printf("Test3 begin:\n");
    char *text = "Hello World3";
    CMystring str1(text);
    CMystring str2,str3;
    printf("The expected string is: %s\n", text);
    printf("The actually result is:");
    str3 = str2=str1;
    str3.print();
    printf("\n");
}
int main() {

    Test1();
    Test2();
    Test3();
    system("pause");
    return 0;
}