STL 迭代器研究 iterator , 自创代码MYList
先来看看链表的实现：
MyList.hpp 代码：
#ifndef __MYLIST__
#define __MYLIST__
#include <assert.h>
using namespace std;
template<class Ty>
struct _Node
{
_Node()
{
memset(&data, 0, sizeof(Ty));
prev = 0;
next = 0;
}
_Node(const Ty& val, _Node *p1, _Node *p2)
{
data = val;
prev = p1;
next = p2;
}
Ty data;
_Node *prev;
_Node *next;
};
template<class Ty>
class _Itor
{
public:
_Node < Ty > * node;//_Node < Ty > 看成是一个类 ，Node
//兼容标准STL
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef std::forward_iterator_tag iterator_category;
typedef _Node < Ty > value_type;
typedef _Node < Ty > * pointer;
typedef _Node < Ty > & reference;
public:
//default construct
_Itor()
{
node = 0;
}
_Itor(_Node<Ty> *val)
{
node = val;
}
//copy construct
_Itor(const _Itor<Ty>& _Right)
{
node = _Right.node;
}
//=
_Itor& operator=(const _Itor<Ty> &_Right)
{
node = _Right.node;
return *this;
}
//
bool operator ==(const _Itor<Ty> &_Right)
{
return node == _Right.node;
}
//
bool operator != (const _Itor<Ty> &_Right)
{
return node != _Right.node;
}
_Itor& operator++()
{
node = node->next;//很明显用到了容器的方法
return *this;
}
_Itor& operator--() //e.g. *(--itor) 操作
{
node = node->prev;
return *this;
}
_Itor & operator+(int n)//后向偏移个数
{
//无法对n 作越界判断
if (n > 0)
{
while (n--)
{
node = node->next;
}
}
return *this;
}
_Itor & operator+=(int n)//后向偏移个数
{
//无法对n 作越界判断
if (n > 0)
{
while (n--)
{
node = node->next;
}
}
return *this;
}
_Itor & operator-(int n)//前向偏移个数
{
if (n > 0)
{
while (n--)
{
node = node->prev;
}
}
return *this;
}
_Itor & operator-=(int n)//前向偏移个数
{
if (n > 0)
{
while (n--)
{
node = node->prev;
}
}
return *this;
}
Ty & operator *()//看来返回引用类型，存取数据皆可 ,* -> 应该返回实际数据
{
return node->data;
}
_Node < Ty > * operator->()
{
return node;
}
};
template<class Ty>
class MYList
{
public:
typedef _Node<Ty> myNode;
typedef _Itor<Ty> myItor;//MYList<Ty> myItor; 等同于 _Itor<Ty>
private:
myNode *_myHead;
size_t _myCount;
private:
myNode* insert(myNode *pos, myNode *node)
{
assert(pos != 0 && node != 0);
myNode *next = pos->next;
pos->next = node;
node->prev = pos;
next->prev = node;
node->next = next;
up_count();
return node;
}
myNode* alloc(const Ty& val)
{
myNode *tmp = new myNode;
tmp->data = val;
tmp->prev = tmp->next = 0;
return tmp;
}
myNode *leaveLink(myNode*pos)//返回下一个
{
assert(pos != _myHead &&pos != 0);
myNode *prev = pos->prev;
myNode *next = pos->next;
prev->next = next;
next->prev = prev;
down_count();
delete pos;
return next;
}
void up_count()
{
_myCount++;
}
void down_count()
{
assert(_myCount > 0);
_myCount--;
}
public:
myNode * getHead()
{
return _myHead;
}
// default construct
void clear()
{
myNode *node = _myHead->next;
while (node->next != node)
{
node = leaveLink(node);
}
}
size_t size()
{
return _myCount;
}
bool isEmpty()
{
return _myCount == 0;
}
MYList()
{
_myHead = new myNode;
_myHead->next = _myHead->prev = _myHead;
_myCount = 0;
}
~MYList()
{
clear();
if (_myHead != NULL)
delete _myHead;
}
MYList(const Ty& val)
{
_myHead = new myNode;
_myHead->next = _myHead->prev = _myHead;
_myCount = 0;
myNode *tmp = alloc(val);
insert(_myHead, tmp);
}
MYList(const Ty& val, size_t count)
{
_myHead = new myNode;
_myHead->next = _myHead->prev = _myHead;
_myCount = 0;
for (size_t i = 0; i < count; ++i)
{
myNode *tmp = alloc(val);
insert(_myHead->prev, tmp); //尾部插入
}
}
//copy construct
MYList(MYList< Ty >& val)
{
_myHead = new myNode;
_myHead->next = _myHead->prev = _myHead;
_myCount = 0;
myNode * head = val.getHead();
myNode *next = head->next;
myNode *tmp = NULL;
while (next != head)
{
myNode *tmp = alloc(next->data);
insert(_myHead->prev, tmp); //尾部插入
next = next->next;
}
}
Ty & operator[] (size_t i)
{
assert(i< _myCount);
size_t j = 0;
myNode *next = _myHead->next;
while (j<i)
{
next = next->next;
j++;
}
return next->data;
}
// front value
Ty& front()
{
return _myHead->next->data;
}
// back value
Ty& back()
{
return _myHead->prev->data;
}
// first itor
myItor begin()
{
return myItor(_myHead->next);
}
myItor end()
{
return myItor(_myHead);
}
void push_front(Ty val)
{
myNode * tmp = alloc(val);
insert(_myHead, tmp); //头部插入
}
void push_back(Ty val)
{
myNode *tmp = alloc(val);
insert(_myHead->prev, tmp); //尾部插入
}
myNode * pop_front()
{
return leaveLink(_myHead->next);
}
myNode * pop_back()
{
return leaveLink(_myHead->prev);
}
void resize(size_t _N)
{
assert(_N<_myCount);
if (_N == 0)
{
clear();
return;
}
//默认将先push_back()的元素删除
if (_N<_myCount && _N>0)
{
int nCutCount = _myCount - _N;
while (nCutCount--)
{
pop_front();
}
}
}
MYList<Ty> & operator =(MYList<Ty>& val)
{
/*_myHead = new myNode;
_myHead->next = _myHead->prev = _myHead;
_myCount = 0;*/
clear();
myNode * head = val.getHead();
myNode *next = head->next;
myNode *tmp = NULL;
while (next != head)
{
myNode *tmp = alloc(next->data);
insert(_myHead->prev, tmp); //尾部插入
next = next->next;
}
return *this;
}
MYList<Ty> & operator += (MYList<Ty>& val)
{
myNode * head = val.getHead();
myNode *next = head->next;
while (next != head)
{
myNode *tmp = alloc(next->data);
insert(_myHead->prev, tmp); //尾部插入
next = next->next;
}
return *this;
}
};
#endif
测试代码：main.cpp
#include "stdafx.h" #include <iostream> #include <algorithm> #include "mylist.hpp" using namespace std; template <class Ty> void ShowMyList(MYList<Ty> & tList, char * sListName) { MYList<Ty>::myItor itor; cout << sListName<<" : "; for (itor = tList.begin(); itor != tList.end(); ++itor) { cout << "[" << itor->data << "]" << "-"; } cout << endl; } template <class Ty> bool FindNullSeat(Ty target) { return target == 'c'; } int _tmain(int argc, _TCHAR* argv[]) { //for use it //s0 MYList < char > tempList; tempList.push_back('A'); tempList.push_back('B'); ShowMyList<char>(tempList,"tempList"); //s1 MYList < char > tempList2('C'); tempList2 += tempList; ShowMyList<char>(tempList2,"tempList2 += "); tempList = tempList2; ShowMyList<char>(tempList, "tempList ="); tempList.pop_front(); ShowMyList<char>(tempList, "tempList pop_front"); cout << "tempList front() =" << tempList.front(); cout << "tempList back() =" << tempList.back(); tempList.push_back('D'); cout << "tempList[2] =" << tempList[2]<<endl; //s2 MYList < char > tempList3('E', 3); ShowMyList<char>(tempList3, "tempList3"); MYList < char > tempList4(tempList); ShowMyList<char>(tempList4, "tempList4"); tempList4.push_front('F'); ShowMyList<char>(tempList4, "tempList4 push_front"); tempList4.pop_back(); ShowMyList<char>(tempList4, "tempList4 pop_back"); tempList4.resize(2); cout << " tempList4.size()= " << tempList4.size() <<"isEmpty="<< tempList4.isEmpty() << endl; ShowMyList<char>(tempList4, "tempList4 resize(2)"); tempList4.clear(); cout << " clear then tempList4.size()= " << tempList4.size() << tempList4.isEmpty() << endl; ShowMyList<char>(tempList4, "tempList4 clear then "); //s3 iterator MYList < char > tempList5; tempList5.push_back('a'); tempList5.push_back('b'); tempList5.push_back('c'); tempList5.push_back('d'); tempList5.push_back('e'); tempList5.push_back('f'); MYList < char >::myItor itor1; MYList < char >::myItor itor2; itor1 = tempList5.begin(); itor1 += 3; //'d' cout << "itor1 += 3;" << " : "; for (; itor1 != tempList5.end(); ++itor1) { cout << "[" << itor1->data << "]" << "-"; } cout << endl; itor2 = tempList5.end(); itor2 -= 2; //'e' cout << "itor1 += 3;" << " : "; for (; itor2 != tempList5.end(); ++itor2) { cout << "[" << itor2->data << "]" << "-"; } cout << endl; ////////---------- MYList < char >::myItor seat = std::find_if(tempList5.begin(), tempList5.end(), FindNullSeat<char>);//只用用std::find_if（）测试通过才能算Iterator编写成功 std::cout << seat->data; getchar(); return 0; }
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