class MyString

Homework_04_01

<1>不要随便加const（==）

<2>看清楚type 红线红线啊~~

/*1) 写一个 MyString 类，使得下面程序的输出结果是：

1. abcd - efgh - abcd -

2. abcd -

3.

4. abcd - efgh -

5. efgh -

6. c

7. abcd -

8. ijAl -

9. ijAl - mnop

10. qrst - abcd -

11. abcd - qrst - abcd - uvw xyz

about

big

me

take

abcd

qrst - abcd -

程序：*/

#include <string.h>

#include <stdlib.h>

#include <string>

#include <iostream>

using namespace std;

class MyString{

char* cptr;

public:

int length(){

return strlen(cptr);

}

MyString(){

cptr = new char[1];

*cptr = 0;

}

MyString(const char * c_){

cptr = new char[strlen(c_) + 1];

strcpy(cptr, c_);

}

MyString operator ()(const int start, const int length){

MyString tmp;

tmp.cptr = new char[length + 1];

for (int i = start; i < start + length; i++){

tmp.cptr[i - start] = cptr[i];

}

tmp.cptr[length] = 0;

return tmp;

}

char & operator[](int subscript){

return cptr[subscript];

}

friend ostream & operator <<(ostream & o, const MyString & c){

o << c.cptr;

return o;

}

friend MyString operator +(MyString c1_, MyString c2_){

char* tmp;

tmp = new char[c1_.length() + 1];

strcpy(tmp, c1_.cptr);

strcat(tmp, c2_.cptr);

MyString c = tmp;

return c;

}

friend MyString operator +(const char * c_, const MyString s_){

MyString tmp = c_;

return tmp + s_;

}

friend MyString operator +(const MyString s_, const char * c_){

MyString tmp = c_;

return s_ + tmp;

}

friend MyString& operator +=(MyString s_, const char *c_){

return s_ + c_;

}

friend bool operator <(MyString s1_, MyString s2_){

int LenMin = 0;

if (s1_.length() < s2_.length())

LenMin = s1_.length();

else

LenMin = s2_.length();

for (int i = 0; i < LenMin; i++){

if (s1_.cptr[i] < s2_.cptr[i])

return true;

else if (s1_.cptr[i]>s2_.cptr[i])

return false;

}

if (s1_.length() >= s2_.length())

return false;

else

return true;

}

friend bool operator ==(MyString s1_, MyString s2_){

if (s1_.length() != s2_.length())

return false;

int Len = s1_.length();

for (int i = 0; i < Len; i++){

if (s1_.cptr[i] != s2_.cptr[i])

return false;

}

return true;

}

friend bool operator >(MyString s1_, MyString s2_){

if (!(s1_ < s2_) && !(s1_ == s2_))

return true;

return false;

}

};

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;

//输出 s1 的下标为 0 的字符开始长度为 4 的子串

cout << s1(0, 4) << endl;

//输出 s1 的下标为 5 的字符开始长度为 10 的子串

cout << s1(5, 10) << endl;

return 0;

}

/*不允许使用 C++的 string 类，完全自己实现 交上去的程序文件名为

mystring1.cpp

提示：如果将程序中所有 "MyString" 用 "string" 替换，那么除了最

后两条红色的语句编译无法通过外，其他语句都没有问题，而且输出和前面给

的结果吻合。也就是说，MyString 类对 string 类的功能扩充只体现在最后两

条语句上面。*/