list是和vector类似的顺序型容器,也是是比vector更为复杂的容器。list是双向带头链表,初始有一个不存数据的头节点,并通过节点内指针将后续节点依次连接起来 。
相较于vector,list特点如下:
(1)list可以按需申请,释放不需要扩容操作,减少内存碎片。
(2)任意位置插入删除的效率是O(1)。
(3)不支持下标随机访问。
(4)cache缓存命中率低。
list结构较为复杂,就list节点来说,list自己本身和list节点不是一样的结构,list包含list节点,因此需要分开设计。
#include<iostream>
using namespace std;
namespace YHY
{
// List的节点类
template<class T>
struct ListNode
{
ListNode(const T& val = T())
{
_val = val;
}
ListNode<T>* _pPre = nullptr;
ListNode<T>* _pNext = nullptr;
T _val;
};
//List的迭代器类
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;
}
Ref operator*()
{
return _pNode->_val;
}
T* operator->()
{
return &(operator*());
}
Self& operator++()
{
_pNode = _pNode->_pNext;
return *this;
}
Self operator++(int)
{
Self old = *this;
_pNode = _pNode->_pNext;
return old;
}
Self& operator--()
{
_pNode = _pNode->_pPre;
return _pNode;
}
Self& operator--(int)
{
Self old = *this;
_pNode = _pNode->_pPre;
return old;
}
bool operator!=(const Self& l)
{
return _pNode != l._pNode;
}
bool operator==(const Self& l) //比较的是节点地址而不是节点内数据,因为比较节点内数据没意义,只有比较地址可以进行遍历的操作
{
return _pNode == l._pNode;
}
PNode _pNode;
};
//list类
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;
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=(const list<T> l)
{
CreateHead();
list(l.begin(), l.end());
return *this;
}
~list()
{
clear();
delete _pHead;
_pHead = nullptr;
}
// List Iterator
const_iterator begin() const
{ return const_iterator(_pHead->_pNext);}
const_iterator end() const
{ return const_iterator(_pHead); }
iterator begin() { return iterator(_pHead->_pNext); }
iterator end() { return iterator(_pHead); }
size_t size() const
{
size_t sum = 0;
const_iterator it = begin();
while (it != end())
{
it++;
sum++;
}
return sum;
}
bool empty()const
{
return _pHead->_pNext == _pHead->_pPre;
}
T& front()
{
return _pHead->_pNext;
}
const T& front()const
{
return _pHead->_pNext;
}
T& back()
{
return _pHead->_pPre;
}
const T& back()const
{
return _pHead->_pPre;
}
// 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
iterator insert(iterator pos, const T& val)
{
PNode newnode = new Node(val);
PNode next = pos._pNode;
PNode pre = next->_pPre;
pre->_pNext = newnode;
newnode->_pPre = pre;
next->_pPre = newnode;
newnode->_pNext = next;
return iterator(newnode);
}
// 删除pos位置的节点,返回该节点的下一个位置
iterator erase(iterator pos)
{
PNode cur = pos._pNode->_pNext;
PNode pre = pos._pNode->_pPre;
cur->_pNext = pre;
pre->_pPre = cur;
pos._pNode->_pNext = nullptr;
pos._pNode->_pPre = nullptr;
delete pos._pNode;
return iterator(cur);
}
void clear()
{
iterator it = begin();
while (it != end())
{
it = erase(it);
}
}
void swap(list<T>& l)
{
std::swap(_pHead, l._pHead);
}
private:
void CreateHead()
{
PNode newhead = new Node;
_pHead = newhead;
_pHead->_pNext = _pHead;
_pHead->_pPre = _pHead;
}
PNode _pHead;
};
};