Question

代码实现String类的方法

编写代码实现String类的
构造函数 析构函数 拷贝构造函数以及APPEND方法

Answer 1

/**-----------------------------------------------------------------------------
* String类的实现
*------------------------------------------------------------------------------
*/
#pragma once

#include <iostream>
#include <cstring>
#include <cassert>

using namespace std;

inline void SafeRelease_Array( const char* s )
{
if( s != NULL )
{
delete []s;
s = NULL;
}
};

class String
{
public:
String(void);
String( unsigned size );
String( const char* );
String( const String& ss );
String( unsigned count, const char& ch );
~String(void);
protected:
char* m_str;
unsigned m_uCount;
public:
// -- 功能函数部分 ------------------- -==---------->>>
void clear();
unsigned size();
bool empty();
const char* c_str() const;
void insert( unsigned , const char& );
void insert( unsigned , const String& );
void push_back( const char& );
void push_front( const char& );
bool erase( const unsigned& );
bool erase( const unsigned&,const unsigned& );

// -- 重载操作符号 ------------------- o(∩_∩)o...哈哈 ---- >>>
String& operator = ( const String& );
String& operator += ( const String& );
String operator + ( const String& );
bool operator == ( const String& );
bool operator < ( const String& );
bool operator > ( const String& );
// 取值
char& operator []( unsigned n );
public:
extern friend ostream& operator << ( ostream& os, const String& ss );
extern friend istream& operator >> ( istream& is, String& ss );
};
/**-----------------------------------------------------------------------------
* String类的实现
*------------------------------------------------------------------------------
*/
#include "String.h"

/**-----------------------------------------------------------------------------
* 默认构造函数
*------------------------------------------------------------------------------
*/
String::String(void):m_str(NULL),m_uCount(0)
{
}

/**-----------------------------------------------------------------------------
* 构造指定大小的对象
*------------------------------------------------------------------------------
*/
String::String( unsigned size ):m_str(NULL),m_uCount(size)
{
if(size)
{
m_str = new char[ size ];
}
}
/**-----------------------------------------------------------------------------
* 按const char* 构造
*------------------------------------------------------------------------------
*/
String::String( const char* str ):m_str(NULL)
{
unsigned n = static_cast<unsigned>(strlen(str));
m_uCount = n;
if( n )
{
m_str = new char[ n ];
strcpy_s( m_str,n+1 ,str );
}
}

/**-----------------------------------------------------------------------------
* 拷贝构造函数
*------------------------------------------------------------------------------
*/
String::String( const String& ss ):m_str(NULL)
{
m_uCount = ss.m_uCount;
if( m_uCount )
{
m_str = new char[ m_uCount ];
strcpy_s( m_str,m_uCount+1 ,ss.m_str );
}
}
/**-----------------------------------------------------------------------------
* 用count个ch构造对象
*------------------------------------------------------------------------------
*/
String::String(unsigned int count, const char &ch):m_str(NULL),m_uCount(count)
{
if( count )
{
m_str = new char[count];
for(unsigned i = 0; i<count;i++)
{
*( m_str+i ) = ch;
}
*( m_str + count ) = '\0';
}
}
/**-----------------------------------------------------------------------------
* 析构函数 --==> 直接调用clear()函数清空
*------------------------------------------------------------------------------
*/
String::~String(void)
{
clear();
}

/**-----------------------------------------------------------------------------
* 删除字符串 将大小置零
*------------------------------------------------------------------------------
*/
void String::clear()
{
if( !m_str ) // = m_str != NULL
{
delete []m_str;
m_str = NULL;
}
m_uCount = 0;
}

/**-----------------------------------------------------------------------------
* 返回大小
*------------------------------------------------------------------------------
*/
unsigned String::size()
{
return m_uCount;
}

/**-----------------------------------------------------------------------------
* 判断是否为空
*------------------------------------------------------------------------------
*/
bool String::empty()
{
return !m_uCount;
}

/**-----------------------------------------------------------------------------
* 转换
*------------------------------------------------------------------------------
*/
const char* String::c_str() const
{
return m_str;
}

/**-----------------------------------------------------------------------------
* 插入字符char
*------------------------------------------------------------------------------
*/
void String::insert( unsigned pos, const char& ch )
{
assert( pos <= m_uCount );

char* t = new char[m_uCount]; // 先暂时将原有字符串放在临时对象中
strcpy_s( t,m_uCount+1,m_str );

m_str = new char[m_uCount +2]; // 重新分配内存

strncpy_s(m_str,m_uCount+2,t,pos); //将前t个字符复制到数组中

*(m_str+pos) = ch; // 插入值

*(m_str+pos+1) = '\0';
/*strcat_s(m_str,m_uCount+2,tmp+pos);*/
strncat_s(m_str,m_uCount+2,t,m_uCount - pos );

m_uCount++;

/*SafeRelease_Array(t);*/ //--==>>一个为解决的bug
}
/**-----------------------------------------------------------------------------
* 插入string
*------------------------------------------------------------------------------
*/
void String::insert( unsigned pos, const String& ss )
{
assert( pos <= m_uCount );

char* t1 = new char[ pos +1 ];
strncpy_s(t1,pos+1,m_str,pos);

char* t2 = new char[ m_uCount - pos + 1 ];
strncpy_s(t2,m_uCount-pos+1,m_str+pos,m_uCount - pos );

m_str = new char[m_uCount + ss.m_uCount + 1];
strcpy_s(m_str,pos+1,t1);
SafeRelease_Array( t1 );

strcat_s(m_str,ss.m_uCount + m_uCount + 1,ss.m_str);
strcat_s(m_str,ss.m_uCount + m_uCount + 1,t2 );
m_uCount += ss.m_uCount;

SafeRelease_Array( t2 );
}
/**-----------------------------------------------------------------------------
* push_back
*------------------------------------------------------------------------------
*/
void String::push_back( const char& ch )
{
insert( m_uCount, ch );
}

/**-----------------------------------------------------------------------------
* push_front
*------------------------------------------------------------------------------
*/
void String::push_front( const char& ch )
{
insert( 0, ch );
}
/**-----------------------------------------------------------------------------
* 删除单个位置
*------------------------------------------------------------------------------
*/
bool String::erase( const unsigned& pos )
{
/*assert( pos < m_uCount );*/
if( pos >= m_uCount )
{
return false;
}
char* t = new char[m_uCount+1];
strcpy_s(t,m_uCount+1,m_str);

SafeRelease_Array(m_str);

m_str = new char[m_uCount];
strncpy_s(m_str,m_uCount,t,pos);
strncat_s(m_str,m_uCount,t+pos+1,m_uCount-pos-1);

m_uCount--;
SafeRelease_Array( t );

return true;
}

/**-----------------------------------------------------------------------------
* 删除连续位置
*------------------------------------------------------------------------------
*/
bool String::erase( const unsigned& begin,const unsigned& end ) // 注意，区间是闭区间，和string类不同，string类是[ )半开半闭区间
{
assert( begin <= end );
if(end>=m_uCount)
return false;
if( begin == end )
{
erase( begin );
}
else
{
unsigned gap = end - begin;
char* t = new char[m_uCount+1];
strcpy_s(t,m_uCount+1,m_str);
SafeRelease_Array(m_str);
int size = m_uCount - gap;
m_str = new char[size];
strncpy_s(m_str,size,t,begin);
strncat_s(m_str,size,t+end+1,size - end-1);

m_uCount -= (gap+1);

SafeRelease_Array( t );
}

return true;
}

/**-----------------------------------------------------------------------------
* 重载 =
*------------------------------------------------------------------------------
*/
String& String::operator = ( const String& ss )
{
clear();
unsigned n = ss.m_uCount;
if( n )
{
m_str = new char[ n + 1 ];
strcpy_s( m_str,n+1,ss.m_str );
m_uCount = ss.m_uCount;
}

return *this;
}
/**-----------------------------------------------------------------------------
* 重载+=
*------------------------------------------------------------------------------
*/
String& String::operator += ( const String& ss )
{
// 这里有一个小bug,如果自己+自己就会崩溃，如： ss += ss; 修改后问题解决
//if( ss.m_uCount )
//{
// char* tmp = new char[ m_uCount + 1 ];
// strcpy_s(tmp,m_uCount+1,m_str);

// delete []m_str;
// m_str = new char[ m_uCount + ss.m_uCount + 1];
// strcpy_s( m_str,m_uCount+1,tmp );
// delete []tmp;
// strcat_s( m_str,m_uCount+ss.m_uCount+1,ss.m_str );

// m_uCount += ss.m_uCount;
//}
if( ss.m_uCount )
{
String temp1(*this);
String temp2(ss);
m_uCount += ss.m_uCount;

delete []m_str;
m_str = new char[ m_uCount + 1 ];
strcpy_s( m_str,temp1.m_uCount+1,temp1.m_str );
strcat_s( m_str,m_uCount + 1,temp2.m_str );
}

return *this;
}
/**-----------------------------------------------------------------------------
* 重载 +
*------------------------------------------------------------------------------
*/
String String::operator + ( const String& ss )
{
if( !ss.m_uCount ) // 如果ss为空则直接返回
{
return *this;
}
else // 充分利用已经存在的+=，^_^ 。。。
{
String temp(*this);
temp += ss;

return temp;
}
}
/**-----------------------------------------------------------------------------
* 重载 ==
*------------------------------------------------------------------------------
*/
bool String::operator == ( const String& ss )
{
if( !strcmp( m_str,ss.m_str ) )
{
return true;
}
else
return false;
//貌似这样有个警告：
//warning C4800: “int”: 将值强制为布尔值“true”或“false”(性能警告)
/*return !static_cast<bool>( strcmp( m_str,ss.m_str ) );*/
}

/**-----------------------------------------------------------------------------
* 重载 <
*------------------------------------------------------------------------------
*/
bool String::operator < ( const String& ss )
{
int mark = strcmp( m_str,ss.m_str );
if( mark < 0 )
return true;
else
return false;
}

/**-----------------------------------------------------------------------------
* 重载 >
*------------------------------------------------------------------------------
*/
bool String::operator > ( const String& ss )
{
// 下面这样是不严密的。。。
//return !( *this < ss );
int mark = strcmp( m_str,ss.m_str );
if( mark > 0 )
return true;
else
return false;
}

/**-----------------------------------------------------------------------------
* 取值 重载[]
*------------------------------------------------------------------------------
*/
char& String::operator [] ( unsigned n )
{
assert( n < m_uCount );

return *(m_str+n);
}
/**-----------------------------------------------------------------------------
* 重载输出运算符
*------------------------------------------------------------------------------
*/
ostream& operator << ( ostream& os, const String& ss )
{
os<<ss.m_str;

return os;
}
/**-----------------------------------------------------------------------------
* 重载输入运算符
*------------------------------------------------------------------------------
*/
istream& operator >> ( istream& is, String& ss ) // 输入时请勿包含空格
{
ss.clear();
is>>ss.m_str;

ss.m_uCount = static_cast<unsigned>(strlen( ss.m_str ));

return is;
}

APPEND就是在末尾insert

Answer 2

给我个木马C程序好吗