为了实现list,我们需要实现三个类
一、List的节点类
cpp
template<class T>
struct ListNode
{
ListNode(const T& val = T())
:_pPre(nullptr)
,_pNext(nullptr)
,_val(val)
{}
ListNode<T>* _pPre;
ListNode<T>* _pNext;
T _val;
};
二、List的迭代器类
cpp
template<class T, class Ref, class Ptr>
class ListIterator
{
typedef ListNode<T>* PNode;
typedef ListIterator<T, Ref, Ptr> Self;
public:
ListIterator(PNode pNode = nullptr)
:_pNode(pNode)
{}
ListIterator(const Self& l)
:_pNode(l._pNode)
{}
T& operator*()
{
return _pNode->_val;
}
T* operator->()
{
return &(_pNode->_val);
}
Self& operator++()//前置++
{
_pNode = _pNode->_pNext;
return *this;
}
Self operator++(int)//后置++
{
Self tmp(*this);
_pNode = _pNode->_pNext;
return tmp;
}
Self& operator--()
{
_pNode = _pNode->_pPre;
return *this;
}
Self& operator--(int)
{
Self tmp(*this);
_pNode = _pNode->_pPre;
return tmp;
}
bool operator!=(const Self& l)
{
return _pNode != l._pNode;
}
bool operator==(const Self& l)
{
return _pNode == l._pNode;
}
PNode _pNode;
};
三、List类
1.数据定义相关
cpp
template<class T>
class list
{
typedef ListNode<T> Node;
typedef Node* PNode;
public:
typedef ListIterator<T, T&, T*> iterator;
typedef ListIterator<T, const T&, const T&> const_iterator;
private:
void CreateHead()//初始化
{
_pHead = new Node;
_pHead->_pNext = _pHead;
_pHead->_pPre = _pHead;
_size = 0;
}
PNode _pHead;//头指针
size_t _size;
};
2.构造函数相关
cpp
public:
///
// List的构造
list()
{
CreateHead();
}
list(int n, const T& value = T())
{
CreateHead();
for (int i = 0; i < n; i++)
{
push_back(value);
}
}
template <class Iterator>
list(Iterator first, Iterator last)
{
CreateHead();
while (first != last)
{
push_back(*first);
first++;
}
}
list(const list<T>& l)
{
CreateHead();
for (auto& e : l)
{
push_back(e);
}
}
list<T>& operator=(list<T> l)
{
swap(l);
return *this;
}
~list()
{
clear();
delete _pHead;
_pHead = nullptr;
}
3.迭代器相关
cpp
///
// List Iterator
iterator begin()
{
return iterator(_pHead->_pNext);
}
iterator end()
{
return iterator(_pHead);
}
const_iterator begin() const
{
return const_iterator(_pHead->_pNext);
}
const_iterator end() const
{
return const_iterator(_pHead);
}
4.容量相关
cpp
///
// List Capacity
size_t size()const
{
return _size;
}
bool empty()const
{
return _size == 0;
}
5.数据访问相关
cpp
// List Access
T& front()
{
return _pHead->_pNext->_val;
}
const T& front()const
{
return _pHead->_pNext->_val;
}
T& back()
{
return _pHead->_pPre->_val;
}
const T& back()const
{
return _pHead->_pPre->_val;
}
6.修改数据相关
cpp
// List Modify
void push_back(const T& val)
{
insert(end(), val);
}
void pop_back()
{
erase(--end());
}
void push_front(const T& val)
{
insert(begin(), val);
}
void pop_front()
{
erase(begin());
}
// 在pos位置前插入值为val的节点
void insert(iterator pos, const T& val)
{
PNode pcur = pos._pNode;
PNode newnode = new Node(val);
PNode prev = pcur->_pPre;
newnode->_pNext = pcur;
newnode->_pPre = prev;
pcur->_pPre = newnode;
prev->_pNext = newnode;
_size++;
}
// 删除pos位置的节点,返回该节点的下一个位置
iterator erase(iterator pos)
{
PNode pdel = pos._pNode;
PNode prev = pdel->_pPre;
PNode next = pdel->_pNext;
next->_pPre = prev;
prev->_pNext = next;
delete pdel;
_size--;
return iterator(next);
}
void clear()
{
iterator it = begin();
while (it != end())
{
it = erase(it);
}
}
void swap(list<T>& l)
{
std::swap(_pHead, l._pHead);
std::swap(_size, l._size);
}
四、测试一下我们自己写的List
所用测试程序test.cpp
cpp
#include"List.h"
using namespace std;
///
// 对模拟实现的list进行测试
// 正向打印链表
template<class T>
void PrintList(const bite::list<T>& l)
{
auto it = l.begin();
while (it != l.end())
{
cout << *it << " ";
++it;
}
cout << endl;
}
// 测试List的构造
void TestBiteList1()
{
cout << "-----------------TestBiteList1()-----------------" << endl;
bite::list<int> l1;
bite::list<int> l2(10, 5);
PrintList(l2);
int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
bite::list<int> l3(array, array + sizeof(array) / sizeof(array[0]));
PrintList(l3);
bite::list<int> l4(l3);
PrintList(l4);
l1 = l4;
PrintList(l1);
}
// PushBack()/PopBack()/PushFront()/PopFront()
void TestBiteList2()
{
cout << "-----------------TestBiteList2()-----------------" << endl;
// 测试PushBack与PopBack
bite::list<int> l;
l.push_back(1);
l.push_back(2);
l.push_back(3);
PrintList(l);
l.pop_back();
l.pop_back();
PrintList(l);
l.pop_back();
cout << l.size() << endl;
// 测试PushFront与PopFront
l.push_front(1);
l.push_front(2);
l.push_front(3);
PrintList(l);
l.pop_front();
l.pop_front();
PrintList(l);
l.pop_front();
cout << l.size() << endl;
}
// 测试insert和erase
void TestBiteList3()
{
cout << "-----------------TestBiteList3()-----------------" << endl;
int array[] = { 1, 2, 3, 4, 5 };
bite::list<int> l(array, array + sizeof(array) / sizeof(array[0]));
auto pos = l.begin();
l.insert(l.begin(), 0);
PrintList(l);
++pos;
l.insert(pos, 2);
PrintList(l);
l.erase(l.begin());
l.erase(pos);
PrintList(l);
// pos指向的节点已经被删除,pos迭代器失效
cout << *pos << endl;
auto it = l.begin();
while (it != l.end())
{
it = l.erase(it);
}
cout << l.size() << endl;
}
int main()
{
TestBiteList1();
TestBiteList2();
TestBiteList3();
return 0;
}