一个c++类的问题

[Buchanan]

这是面试题让我写的类，hr说“GetLength你是数string的长度，但应该直接返回sizeStr，不仅速度会快很多，这也是用Class 来实现的意义之一。”
这话是什么意思啊？不数string的长度能直接返回sizeStr么？

#include <stdio.h>

class MyString{
public:
MyString();
MyString(char *str) //consturct the string
{
pStr=str;
}
~MyString(){};

int GetSizeStr();
void SetLength(int len);
int GetLength();
void Output(char *deal);
void Add(char add);
void Append(char *append);
int Find(char find); //find a char
int Find(char *strFind); //find a string

private:
char *pStr;
int sizeStr;
};

int MyString::GetLength() //get the length of string
{
sizeStr=0;
char *p=pStr;
while (*p!='\0')
{
sizeStr++;
p++;
}
return sizeStr;
}

void MyString::SetLength(int len) //set the length
{
sizeStr=len;
char *p=pStr;
while (len>0) //keep the string[0~sizeStr-1]
{
p++;
len--;
}
*p='\0';
p++;
while (*p!='\0') //set the char after the new length as '\0'
{
*p='\0';
p++;
}
printf("The string after setting length is: %s\n",pStr);
}

int MyString::GetSizeStr() //get sizeStr
{
return sizeStr;
}

void MyString::Output(char *deal) //output the string
{
printf("The string after %s is: %s\n",deal,pStr);
}

void MyString::Add(char add) //append a char to the end of string
{
char *p=pStr;
while (*p!='\0') p++;
*p=add;
}

void MyString::Append(char *append) //append a char to the end of string
{
char *p=pStr;
char *pApp=append;
while (*p!='\0') p++;
while (*pApp!='\0')
{
*p=*pApp; //append the string char by char
pApp++;
p++;
}
}

int MyString::Find(char find) //find char
{
int pos=0;
char *p=pStr;
while (*p!=find&&*p!='\0') //find through the pStr
{
p++;
pos++;
}
if (*p==find) return pos; //found the char
else return -1;
}

int MyString::Find(char *strFind) //find string
{
int pos=0;
char *p=pStr;
char *pTextFind=strFind;
while (*p!='\0')
{
if (*strFind==*p) //found the first char is matched
{
char *pSearch=p;
pTextFind=strFind; //reset the pointer point to string wanna find
while (*pSearch==*pTextFind&&*pSearch!='\0') //matching
{
pSearch++;
pTextFind++;
}
if (*pTextFind=='\0') return pos; //match all of strFind, found the string
}
pos++;
p++;
}
return -1;
}


main()
{
char strInput[999]=""; //the string input
char append[999]=""; //the string want to append to the end
char strFind[999]=""; //a string want to find in the string
char add;
char find;
int len=0;

printf("Input a String for initilizing: ");
scanf("%s",strInput);
MyString myString(strInput); //initilize the string

printf("The length of the string is %d",myString.GetLength()); //test of GetLength

printf("\n\nPlease input the length you want to set:"); //test of SetLength
scanf("%d",&len);
myString.SetLength(len);
printf("The length has been set to: %d\n",myString.GetSizeStr());

printf("\nInput the char you want to append to the end of string:"); //test of Add
scanf("%s",&add);
myString.Add(add);
myString.Output("ADDED is: ");

printf("\nInput the string you want to append to the end of string:"); //test of Append
scanf("%s",append);
myString.Append(append);
myString.Output("APPEND is: ");

printf("\nInput the char you want to find:"); //test of find(char f)
scanf("%s",&find);
printf("The position of the CHAR you want to find is %d\n",myString.Find(find));

printf("\nInput the string you want to find:"); //test of find(char *str)
scanf("%s",strFind);
printf("The position of the STRING you want to find is %d\n",myString.Find(strFind));
return 0;
}

[独孤过儿]

可以在类里面加个计数器...

[p0303230]

不是有sizestr
还要用函数干嘛啊

[Buchanan]

sizeStr直接是string的长度？不用计算？

[hxxwcc]

you can modify the length of a string(stored in an int number) each time you modified the length of string to avoid computing the length each time.

[Buchanan]

还是不明白。

[iambic]

记下来，就用不着每次都手动数了。