C++探究transform算法

transform函数原型

1.

template<class _InIt,
	class _OutIt,
	class _Fn1> inline
	_OutIt transform(_InIt _First, _InIt _Last,
		_OutIt _Dest, _Fn1 _Func)
	{	// transform [_First, _Last) with _Func
	_DEPRECATE_UNCHECKED(transform, _Dest);
	return (_Transform_no_deprecate(_First, _Last, _Dest, _Func));
	}

2.

template<class _InIt1,
	class _InIt2,
	class _OutIt,
	class _Fn2> inline
	_OutIt transform(_InIt1 _First1, _InIt1 _Last1,
		_InIt2 _First2, _OutIt _Dest, _Fn2 _Func)
	{	// transform [_First1, _Last1) and [_First2, ...) with _Func
	_DEFINE_DEPRECATE_UNCHECKED(transform);
	_USE_DEPRECATE_UNCHECKED(_First2);
	_USE_DEPRECATE_UNCHECKED(_Dest);
	return (_Transform_no_deprecate(_First1, _Last1, _First2, _Dest, _Func));
	}

3.

 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
template<class _InIt,
	class _OutTy,
	size_t _OutSize,
	class _Fn1> inline
	_OutTy *transform(_InIt _First, _InIt _Last,
		_OutTy (&_Dest)[_OutSize], _Fn1 _Func)
	{	// transform [_First, _Last) with _Func, array dest
	return (_Unchecked(
		_Transform_no_deprecate(_First, _Last,
			_Array_iterator<_OutTy, _OutSize>(_Dest), _Func)));
	}
 #endif /* _ITERATOR_DEBUG_ARRAY_OVERLOADS */

4-6.

 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
template<class _InIt1,
	class _InTy,
	size_t _InSize,
	class _OutIt,
	class _Fn2> inline
	_OutIt transform(_InIt1 _First1, _InIt1 _Last1,
		_InTy (&_First2)[_InSize], _OutIt _Dest, _Fn2 _Func)
	{	// transform [_First1, _Last1) and [_First2, ...), array input
	_DEPRECATE_UNCHECKED(transform, _Dest);
	return (_Transform_no_deprecate(_First1, _Last1,
		_Array_iterator<_InTy, _InSize>(_First2), _Dest, _Func));
	}

template<class _InIt1,
	class _InIt2,
	class _OutTy,
	size_t _OutSize,
	class _Fn2> inline
	_OutTy *transform(_InIt1 _First1, _InIt1 _Last1,
		_InIt2 _First2, _OutTy (&_Dest)[_OutSize], _Fn2 _Func)
	{	// transform [_First1, _Last1) and [_First2, ...), array dest
	_DEPRECATE_UNCHECKED(transform, _First2);
	return (_Unchecked(
		_Transform_no_deprecate(_First1, _Last1,
			_First2, _Array_iterator<_OutTy, _OutSize>(_Dest), _Func)));
	}

template<class _InIt1,
	class _InTy,
	size_t _InSize,
	class _OutTy,
	size_t _OutSize,
	class _Fn2> inline
	_OutTy *transform(_InIt1 _First1, _InIt1 _Last1,
		_InTy (&_First2)[_InSize], _OutTy (&_Dest)[_OutSize], _Fn2 _Func)
	{	// transform [_First1, _Last1) and [_First2, ...), array input/dest
	return (_Unchecked(
		_Transform_no_deprecate(_First1, _Last1,
			_Array_iterator<_InTy, _InSize>(_First2),
			_Array_iterator<_OutTy, _OutSize>(_Dest), _Func)));
	}
 #endif /* _ITERATOR_DEBUG_ARRAY_OVERLOADS */

暂时只研究前面2种

1.

#include <iostream>
#include<algorithm>
#include <functional>
#include <vector>

using namespace std;
class Ticket
{
public:
	Ticket()
	{
		;
	}
	int num;
	int id;
	char zimu;
};
class MyShow_transform
{
public:
	Ticket* operator()(Ticket* t)
	{
		if (t->zimu == 'A')
		{
			cout << "车号：" << t->num << "座位：" << t->id << "排" << t->zimu << "座" << endl;
			return t;
		}
		t->num = 0;
		return t;
	}
};
void show(Ticket* t)
{
	if(t->num != 0)
		cout<< t->num << "车" << t->id << "排" << t->zimu << "座" << endl;
	return;
}
void test_transform()
{
	vector<Ticket*> v1,v2,v3;

	for (int num = 0; num < 2; num++)
	{
		for (int id = 0; id < 5; id++)
		{
			for (int i = 0; i < 5; i++)
			{
				Ticket *tmp = new Ticket;
				tmp->num = num+1;
				tmp->id = id+1;
				tmp->zimu = 'A' + i;
				v1.push_back(tmp);
			}
		}
	}
	v2.resize(v1.size());
	transform(v1.begin(), v1.end(), v2.begin(),MyShow_transform() );
	cout << "-------------------------------------------------------------------" << endl;
	for_each(v2.begin(), v2.end(), show);
	for (vector<Ticket*>::iterator it = v1.begin(); it != v1.end(); )
	{
		delete (*it);
		it = v1.erase(it);
		it++;
	}
}

增加函数适配器

#include <iostream>
#include<algorithm>
#include <functional>
#include <vector>

using namespace std;
class Ticket
{
public:
	Ticket()
	{
		;
	}
	int num;
	int id;
	char zimu;
};
class MyShow_transform : public std::binary_function<Ticket*, char, Ticket*>
{
public:
	Ticket* operator()(const Ticket* t, const char c)const
	{
		Ticket* p = nullptr;
		if (t->zimu == c)
		{
			cout << "车号：" << t->num << "座位：" << t->id << "排" << t->zimu << "座" << endl;
			p = const_cast<Ticket *>(t);
			return p;
		}
		if(p != nullptr)
			p->num = 0;
		return p;
	}
};
void show(Ticket* t)
{
	if (t == nullptr)
		return;
	if(t->num != 0)
		cout<< t->num << "车" << t->id << "排" << t->zimu << "座" << endl;
	return;
}
void test_transform()
{
	vector<Ticket*> v1,v2,v3;

	for (int num = 0; num < 2; num++)
	{
		for (int id = 0; id < 5; id++)
		{
			for (int i = 0; i < 5; i++)
			{
				Ticket *tmp = new Ticket;
				tmp->num = num+1;
				tmp->id = id+1;
				tmp->zimu = 'A' + i;
				v1.push_back(tmp);
			}
		}
	}
	v2.resize(v1.size());
	transform(v1.begin(), v1.end(), v2.begin(),bind2nd( MyShow_transform(),'A' ));
	cout << "-------------------------------------------------------------------" << endl;
	for_each(v2.begin(), v2.end(), show);
	for (vector<Ticket*>::iterator it = v1.begin(); it != v1.end(); )
	{
		delete (*it);
		it = v1.erase(it);
		it++;
	}
}

void main()
{
	test_transform();
	cout << endl;
	cout << "hello" << endl;
	system("pause");
}

　　

2.增加一个vector

#include <iostream>
#include<algorithm>
#include <functional>
#include <vector>

using namespace std;
class Ticket
{
public:
	Ticket()
	{
		;
	}
	int num;
	int id;
	char zimu;
};
class MyShow_transform : public std::binary_function<Ticket*, char, Ticket*>
{
public:
	Ticket* operator()(const Ticket* t, const char c)const
	{
		Ticket* p = nullptr;
		if (t->zimu == c)
		{
			cout << "车号：" << t->num << "座位：" << t->id << "排" << t->zimu << "座" << endl;
			p = const_cast<Ticket *>(t);
			return p;
		}
		if(p != nullptr)
			p->num = 0;
		return p;
	}
};
class MyShow_transformadv : public std::binary_function<Ticket*, Ticket*, Ticket*>
{
public:
	Ticket* operator()(const Ticket* t1, const Ticket* t2)const
	{
		Ticket* p = nullptr;
		p = const_cast<Ticket *>(t1);
		if (t2 == nullptr)
			return p;
		if (t1->num == t2->num)
		{
			cout << "车号：" << t1->num << "座位：" << t1->id << "排" << t1->zimu << "座" << endl;
			return p;
		}
		if (p != nullptr)
			p->num = 0;
		return p;
	}
};
void show(Ticket* t)
{
	if (t == nullptr)
		return;
	if(t->num != 0)
		cout<< t->num << "车" << t->id << "排" << t->zimu << "座" << endl;
	return;
}
void test_transform()
{
	vector<Ticket*> v1,v2,v3;

	for (int num = 0; num < 2; num++)
	{
		for (int id = 0; id < 5; id++)
		{
			for (int i = 0; i < 5; i++)
			{
				Ticket *tmp = new Ticket;
				tmp->num = num+1;
				tmp->id = id+1;
				tmp->zimu = 'A' + i;
				v1.push_back(tmp);
			}
		}
	}
	v2.resize(v1.size());
	cout << "v2-------------------------------------------------------------------" << endl;
	transform(v1.begin(), v1.end(), v2.begin(),bind2nd( MyShow_transform(),'A' ));
	v3.resize(v1.size());
	cout << "v3-------------------------------------------------------------------" << endl;
	transform(v1.begin(), v1.end(), v2.begin(),v3.begin(), MyShow_transformadv());
	cout << "-------------------------------------------------------------------" << endl;

	for (vector<Ticket*>::iterator it = v1.begin(); it != v1.end(); )
	{
		delete (*it);
		it = v1.erase(it);
		it++;
	}
}

void main()
{
	test_transform();
	cout << endl;
	cout << "hello" << endl;
	system("pause");
}