原题题目
#include <cstdlib>
#include <iostream>
using namespace std;
int strlen(const char * s)
{
int i = 0;
for(; s[i]; ++i);
return i;
}
void strcpy(char * d,const char * s)
{
int i = 0;
for( i = 0; s[i]; ++i)
d[i] = s[i];
d[i] = 0;
}
int strcmp(const char * s1,const char * s2)
{
for(int i = 0; s1[i] && s2[i] ; ++i) {
if( s1[i] < s2[i] )
return -1;
else if( s1[i] > s2[i])
return 1;
}
return 0;
}
void strcat(char * d,const char * s)
{
int len = strlen(d);
strcpy(d+len,s);
}
class MyString
{
};
int CompareString( const void * e1, const void * e2)
{
MyString * s1 = (MyString * ) e1;
MyString * s2 = (MyString * ) e2;
if( * s1 < *s2 )
return -1;
else if( *s1 == *s2)
return 0;
else if( *s1 > *s2 )
return 1;
}
int main()
{
MyString s1("abcd-"),s2,s3("efgh-"),s4(s1);
MyString SArray[4] = {
"big","me","about","take"};
cout << "1. " << s1 << s2 << s3<< s4<< endl;
s4 = s3;
s3 = s1 + s3;
cout << "2. " << s1 << endl;
cout << "3. " << s2 << endl;
cout << "4. " << s3 << endl;
cout << "5. " << s4 << endl;
cout << "6. " << s1[2] << endl;
s2 = s1;
s1 = "ijkl-";
s1[2] = 'A' ;
cout << "7. " << s2 << endl;
cout << "8. " << s1 << endl;
s1 += "mnop";
cout << "9. " << s1 << endl;
s4 = "qrst-" + s2;
cout << "10. " << s4 << endl;
s1 = s2 + s4 + " uvw " + "xyz";
cout << "11. " << s1 << endl;
qsort(SArray,4,sizeof(MyString),CompareString);
for( int i = 0;i < 4;i ++ )
cout << SArray[i] << endl;
cout << s1(0,4) << endl;
cout << s1(5,10) << endl;
return 0;
}
代码实现
char* str;
public:
MyString()
{
str = new char[1];
str[0] = '\0';
}
MyString(const char* a)
{
str = new char[strlen(a)+1];
strcpy(str,a);
}
MyString(const MyString& a)
{
str = new char[strlen(a.str)+1];
strcpy(str,a.str);
}
~MyString()
{
if(str)
delete []str;
}
friend ostream& operator<<(ostream& os,const MyString& a)
{
os<<a.str;
return os;
}
MyString& operator = (const MyString& a)
{
delete []str;
str = new char[strlen(a.str)+1];
strcpy(str,a.str);
return *this;
}
MyString operator +(MyString & a)
{
MyString ret;
ret.str = new char[strlen(str)+strlen(a.str)+1];
int str1 = strlen(str),str2 = strlen(a.str);
for(int i=0;i<str1+str2+1;i++)
ret.str[i] = '\0';
strcpy(ret.str,str);
strcat(ret.str,a.str);
return ret;
}
MyString operator + (const char* s)
{
MyString ret;
ret.str = new char[strlen(s)+strlen(str)+1];
int str1 = strlen(s),str2 = strlen(str);
for(int i=0;i<str1+str2+1;i++)
ret.str[i] = '\0';
strcpy(ret.str,str);
strcat(ret.str,s);
return ret;
}
friend MyString operator +(const char* s,const MyString& a)
{
MyString ret;
ret.str = new char[strlen(s)+strlen(a.str)+1];
int str1 = strlen(s),str2 = strlen(a.str);
for(int i=0;i<str1+str2+1;i++)
ret.str[i] = '\0';
strcpy(ret.str,s);
strcat(ret.str,a.str);
return ret;
}
char& operator[](int n)
{
return str[n];
}
void operator+=(const char* s)
{
strcat(str,s);
}
int operator<(const MyString& a)
{
return str[0]<a.str[0];
}
int operator==(const MyString& a)
{
return str[0]==a.str[0];
}
int operator>(const MyString& a)
{
return str[0]>a.str[0];
}
MyString operator()(int tempstart,int tempend)
{
MyString ret;
ret = new char[tempend+1];
for(int i=0;i<tempend;i++)
ret[i] = '\0';
strcpy(ret.str,str+tempstart);
ret.str[tempend] = '\0';
return ret;
}