c++primer plus 清单12.4，12.5 ，12.6 .

最新推荐文章于 2023-12-29 19:41:03 发布

原创最新推荐文章于 2023-12-29 19:41:03 发布 · 242 阅读

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CC 4.0 BY-SA版权

本文详细介绍了使用C++实现自定义字符串类的过程，包括构造函数、赋值操作符、下标运算符等关键成员函数的设计，以及比较运算符和输入输出流的重载。通过实例展示了字符串对象的创建、赋值、比较和读写操作。

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首先
#include
#ifndef STRNGBAD_H_
#define STRNGBAD_H_
using std::ostream;
using std::istream;
class String
{
private:
char*str;
int len;
static int num_string;
static const int CILIM = 80;
public:
String(const char *s);
String();
String(const String&);
~String();
int length() { return len; }
String & operator=(const String&);
String & operator=(const char *);
char & operator[](int i);
const char & operator[](int i)const;

   friend bool operator<(const String&st, const String&st2);
   friend bool operator>(const String&st1, const String&st2);
   friend bool operator==(const String&st, const String&st2);
   friend ostream& operator<<(ostream&os, const String&st);
   friend istream&operator>>(istream&is,  String &st);
   static int HowMany();

};

#endif
其次

#define _CRT_SECURE_NO_WARNINGS
#include “strngbad.h”
#include
int String::num_string = 0;
using std::cin;
using std::cout;
String::String(const char * s)
{
len = std::strlen(s);
str = new char[len + 1];
std::strcpy(str, s);
num_string++;
std::cout << num_string << “:”"<<str
<< "“object created \n”;

}

String::String()
{
len = 4;
str = new char[1];
str[0] = ‘\n’;
num_string++;
}

String::String(const String &st)
{
num_string++;
len =st.len;
str = new char[len+1];
std::strcpy(str, st.str);
std::cout << num_string << “：”" << str
<< “” object created\n";

}

String::~String()
{
std::cout << “”" << str << "“object delected,”;
–num_string;
std::cout << num_string << “left\n”;
delete[]str;
}

String & String::operator=(const String &st)
{
if (this == &st)
return *this;
delete[]str;
len = st.len;
str = new char[len + 1];
std::strcpy(str, st.str);
return *this;

// TODO: 在此处插入 return 语句

}

String & String::operator=(const char *s)
{
delete[]str;
len = std::strlen(s);
str = new char[len + 1];
std::strcpy(str, s);
return *this;
// TODO: 在此处插入 return 语句
}

char & String::operator[](int i)
{
return str[i];

// TODO: 在此处插入 return 语句

}

const char & String::operator[](int i) const
{
return str[i];
// TODO: 在此处插入 return 语句
}

int String::HowMany()
{
return num_string;

}

bool operator<(const String & st1, const String & st2)
{
return (std::strcmp(st1.str,st2.str)<0);
}

bool operator>(const String & st1, const String & st2)
{
return st2 < st1;
}

bool operator==(const String & st1, const String & st2)
{
return (std::strcmp(st1.str, st2.str)==0);
}

ostream &operator<<(ostream & os, const String & st)
{

	os << st.str;
	return os;
	// TODO: 在此处插入 return 语句

}

istream & operator>>(istream & is, String & st)
{
char temp[String::CILIM];
is.get(temp, String::CILIM);
if (is)
st = temp;
while (is&&is.get() != ‘\n’)
continue;
return is;
// TODO: 在此处插入 return 语句
}

最后
#include
using std::cout;
#include"strngbad.h"
const int Arsize = 10;
const int maxlen = 81;

int main()
{
using std::cin;
using std::cout;

using std::endl;
String name;
cout << "hi,what's your name";
cin >> name;
cout << name << ",please enter up to " << Arsize
	<< "short saying " << "empty line to quit:\n";
String saying[Arsize];
char temp[maxlen];
int i;
for (i = 0;i < Arsize;++i)
{
	cout << i + 1 << ":";
	cin.get(temp, maxlen);
	while (cin&&cin.get() != '\n')
		continue;
	if (!cin || temp[0] == '\0')break;
	else
		saying[i] = temp;
}
int total = i;
if(total>0)
{
	cout << "here are you saying:\n";
	for (i = 0;i < total;i++)
		cout << saying[i][0] << ":" << saying[i] << endl;
	int shortest=0;
	int first = 0;
	for (i = 0;i < total;++i)
	{
		if (saying[i].length() < saying[shortest].length())
			shortest = i;
		if (saying[i] < saying[first])
			first = i;
	}cout << "shortest saying:\n" <<saying[shortest]<<endl;
	cout << "first alphabetically :\n"<<saying[first]<<endl;
		cout << "this program used " << String::HowMany()
			<<"String objects .Bye.\n";

}
else
	cout << "No input! Bye.\n";
system("pause");

return 0;
}