泛型算法系列35:set_difference()&&set_intersection()&&set_symmetric_difference()&&set_union()

#include <algorithm>
#include <set>
#include <string>
#include <iostream>
#include <functional>

using namespace std;
/************************************************************************/
/*                                                                      */
template<class _InIt1, class _InIt2, class _OutIt> inline
_OutIt my_Set_union(_InIt1 _First1, _InIt1 _Last1,
_InIt2 _First2, _InIt2 _Last2, _OutIt _Dest)
{	// OR sets [_First1, _Last1) and [_First2, _Last2), using operator<
_DEBUG_ORDER(_First1, _Last1);
_DEBUG_ORDER(_First2, _Last2);
_DEBUG_POINTER(_Dest);
for (; _First1 != _Last1 && _First2 != _Last2; )
if (_DEBUG_LT(*_First1, *_First2))
*_Dest++ = *_First1, ++_First1;
else if (*_First2 < *_First1)
*_Dest++ = *_First2, ++_First2;
else
*_Dest++ = *_First1, ++_First1, ++_First2;
_Dest = _STDEXT unchecked_copy(_First1, _Last1, _Dest);
return (_STDEXT unchecked_copy(_First2, _Last2, _Dest));
}

template<class _InIt1, class _InIt2, class _OutIt> inline
_OutIt my_Set_intersection(_InIt1 _First1, _InIt1 _Last1,
_InIt2 _First2, _InIt2 _Last2, _OutIt _Dest)
{	// AND sets [_First1, _Last1) and [_First2, _Last2), using operator<
_DEBUG_ORDER(_First1, _Last1);
_DEBUG_ORDER(_First2, _Last2);
_DEBUG_POINTER(_Dest);
for (; _First1 != _Last1 && _First2 != _Last2; )
if (_DEBUG_LT(*_First1, *_First2))
++_First1;
else if (*_First2 < *_First1)
++_First2;
else
*_Dest++ = *_First1++, ++_First2;
return (_Dest);
}

template<class _InIt1, class _InIt2, class _OutIt> inline
_OutIt my_Set_difference(_InIt1 _First1, _InIt1 _Last1,
_InIt2 _First2, _InIt2 _Last2, _OutIt _Dest)
{	// take set [_First2, _Last2) from [_First1, _Last1), using operator<
_DEBUG_ORDER(_First1, _Last1);
_DEBUG_ORDER(_First2, _Last2);
_DEBUG_POINTER(_Dest);
for (; _First1 != _Last1 && _First2 != _Last2; )
if (_DEBUG_LT(*_First1, *_First2))
*_Dest++ = *_First1, ++_First1;
else if (*_First2 < *_First1)
++_First2;
else
++_First1, ++_First2;
return (_STDEXT unchecked_copy(_First1, _Last1, _Dest));
}

template<class _InIt1,
class _InIt2,
class _OutIt> inline
_OutIt my_Set_symmetric_difference(_InIt1 _First1, _InIt1 _Last1,
_InIt2 _First2, _InIt2 _Last2, _OutIt _Dest)
{	// XOR sets [_First1, _Last1) and [_First2, _Last2), using operator<
_DEBUG_ORDER(_First1, _Last1);
_DEBUG_ORDER(_First2, _Last2);
_DEBUG_POINTER(_Dest);
for (; _First1 != _Last1 && _First2 != _Last2; )
if (_DEBUG_LT(*_First1, *_First2))
*_Dest++ = *_First1, ++_First1;
else if (*_First2 < *_First1)
*_Dest++ = *_First2, ++_First2;
else
++_First1, ++_First2;
_Dest = _STDEXT unchecked_copy(_First1, _Last1, _Dest);
return (_STDEXT unchecked_copy(_First2, _Last2, _Dest));
}
/************************************************************************/
/*
* generates:
set #1 elements:
Eeyore Piglet Pooh Tigger
set #2 elements:
Heffalump Pooh Woozles
set_union() elements:
Eeyore Heffalump Piglet Pooh Tigger Woozles
set_intersection() elements:
Pooh
set_difference() elements:
Eeyore Piglet Tigger
set_symmetric_difference() elements:
Eeyore Heffalump Piglet Tigger Woozles
*/
int main()
{
string str1[] = { "Pooh", "Piglet", "Tigger", "Eeyore" };
string str2[] = { "Pooh", "Heffalump", "Woozles" };
ostream_iterator< string >  ofile( cout, " " );
set<string,less<string>,allocator<string>> set1( str1, str1+4 );
set<string,less<string>,allocator<string>> set2( str2, str2+3 );
cout << "set #1 elements:/n/t";
copy( set1.begin(), set1.end(), ofile ); cout <<"/n/n";
cout << "set #2 elements:/n/t";
copy( set2.begin(), set2.end(), ofile ); cout << "/n/n";
set<string,less<string>,allocator<string>> res;
//並集
my_Set_union( set1.begin(), set1.end(),
set2.begin(), set2.end(),
inserter( res, res.begin() ));
cout << "set_union() elements:/n/t";
copy( res.begin(), res.end(), ofile ); cout << "/n/n";
res.clear();

//交集
set_intersection( set1.begin(), set1.end(),
set2.begin(), set2.end(),
inserter( res, res.begin() ));
cout << "set_intersection() elements:/n/t";
copy( res.begin(), res.end(), ofile ); cout << "/n/n";
res.clear();

//差集
my_Set_difference( set1.begin(), set1.end(),
set2.begin(), set2.end(),
inserter( res, res.begin() ));
cout << "set_difference() elements:/n/t";
copy( res.begin(), res.end(), ofile ); cout << "/n/n";
res.clear();

//対称差集
my_Set_symmetric_difference( set1.begin(), set1.end(),
set2.begin(), set2.end(),
inserter( res, res.begin() ));
cout << "set_symmetric_difference() elements:/n/t";
copy( res.begin(), res.end(), ofile ); cout << "/n/n";

return 0;
}

通过algorithm中提供的set_intersection、set_union、set_difference、set_symmetric_difference四个函数，可以方便的实现集合的交、并、差、对称差操作