目录
在上一节已经了解list在库中的用法,在这里实现list的底层逻辑
一.list类
1.list的创建节点
template<class T>
struct __list_node
{
__list_node* _next;
__list_node* _prev;
T _data;
__list_node(const T& x = T()) :_data(x), _next(nullptr), _prev(nullptr) {}
};
2.list迭代器的运算符操作
template<class T, class Ref, class Ptr>
struct __list_iterator
{
typedef __list_node<T> Node;
typedef __list_iterator<T, Ref, Ptr> Self;
Node* _node;
__list_iterator(Node* node):_node(node) {}
Ref operator*()
{
return _node->_data;
}
Ptr operator->()
{
return &_node->_data;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
//_node = _node->_next;
++(*this);
return tmp;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator--(int)
{
Self tmp(*this);
//_node = _node->_prev;
--(*this);
return tmp;
}
bool operator!=(const Self& it)
{
return _node != it._node;
}
bool operator==(const Self& it)
{
return _node == it._node;
}
};
3.list的构造函数及析构
1.list的构造函数
因为list是双向带头循环链表,所以我们只需要让头节点的prev和next都指向头节点
//双向带头循环链表
list()
{
_head = new Node;
_head->_next = _head;
_head->_prev = _head;
}
2.list的拷贝构造
拷贝构造时我们需要创建一个新的节点,将值依次插入尾部即可,可以通过迭代器遍历,也可以通过范围for
list(const list<T>& lt)
{
_head = new Node;
_head->_next = _head;
_head->_prev = _head;
/*const_iterator it = lt.begin();
while (it != lt.end())
{
push_back(*it);
++it;
}*/
for (auto ch : lt)
push_back(ch);
}
3.list的赋值
赋值是不需要创建新节点的,因为已经有了,所以只需要插入值即可
list<T>& operator=(const list<T>& lt)
{
if (this != <)
{
clear();
for (auto ch : lt)
push_back(ch);
}
return *this;
}
4.list的析构
析构在这里我们用到clear函数,clear是清空所以数据,只留头节点,但是析构头节点也要释放
~list()
{
clear();
delete _head;
_head = nullptr;
}
void clear()
{
iterator it = begin();
while (it != end())
{
erase(it++);
}
}
4.list的迭代器
iterator begin()
{
return iterator(_head->_next);
}
iterator end()
{
return iterator(_head);
}
const_iterator begin() const
{
return const_iterator(_head->_next);
}
const_iterator end() const
{
return const_iterator(_head);
}
5.list的插入及删除
push_back
尾部插入一个值时只需要将节点前后连接,并更新头节点的prev
void push_back(const T& x)
{
Node* tail = _head->_prev;
Node* newnode = new Node(x);
tail->_next = newnode;
newnode->_prev = tail;
newnode->_next = _head;
_head->_prev = newnode;
}
insert
任意插入一个值,我们需要创建一个节点,并将其与前后节点连接
void insert(iterator pos, const T& x)
{
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* newnode = new Node(x);
//prev newnode cur
prev->_next = newnode;
newnode->_prev = prev;
newnode->_next = cur;
cur->_prev = newnode;
}
当我们实现了insert后,对于push_back和push_front都可以通过调用insert实现
void push_back(const T& x)
{
insert(end(), x);
}
void push_front(const T& x)
{
insert(begin(), x);
}
erase
对于erase来说,我们只需要找到删除节点的prev和next,将他们两个连接,删除当前节点即可
void erase(iterator pos)
{
assert(pos != end());
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* next = cur->_next;
delete cur;
prev->_next = next;
next->_prev = prev;
}
实现erase后,pop_back和pop_front调用erase即可
void pop_back()
{
erase(--end());
}
void pop_front()
{
erase(begin());
}
二.整体代码
1.list.h
#pragma once
#include <iostream>
#include<assert.h>
using namespace std;
namespace wzyl
{
template<class T>
struct __list_node
{
__list_node* _next;
__list_node* _prev;
T _data;
__list_node(const T& x = T()) :_data(x), _next(nullptr), _prev(nullptr) {}
};
template<class T, class Ref, class Ptr>
struct __list_iterator
{
typedef __list_node<T> Node;
typedef __list_iterator<T, Ref, Ptr> Self;
Node* _node;
__list_iterator(Node* node):_node(node) {}
Ref operator*()
{
return _node->_data;
}
Ptr operator->()
{
return &_node->_data;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
//_node = _node->_next;
++(*this);
return tmp;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator--(int)
{
Self tmp(*this);
//_node = _node->_prev;
--(*this);
return tmp;
}
bool operator!=(const Self& it)
{
return _node != it._node;
}
bool operator==(const Self& it)
{
return _node == it._node;
}
};
template<class T>
class list
{
typedef __list_node<T> Node;
public:
typedef __list_iterator<T, T&, T*> iterator;
typedef __list_iterator<T, const T&, const T*> const_iterator;
iterator begin()
{
return iterator(_head->_next);
}
iterator end()
{
return iterator(_head);
}
const_iterator begin() const
{
return const_iterator(_head->_next);
}
const_iterator end() const
{
return const_iterator(_head);
}
//双向带头循环链表
list()
{
_head = new Node;
_head->_next = _head;
_head->_prev = _head;
}
list(const list<T>& lt)
{
_head = new Node;
_head->_next = _head;
_head->_prev = _head;
/*const_iterator it = lt.begin();
while (it != lt.end())
{
push_back(*it);
++it;
}*/
for (auto ch : lt)
push_back(ch);
}
list<T>& operator=(const list<T>& lt)
{
if (this != <)
{
clear();
for (auto ch : lt)
push_back(ch);
}
return *this;
}
~list()
{
clear();
delete _head;
_head = nullptr;
}
void clear()
{
iterator it = begin();
while (it != end())
{
erase(it++);
}
}
void push_back(const T& x)
{
/*Node* tail = _head->_prev;
Node* newnode = new Node(x);
tail->_next = newnode;
newnode->_prev = tail;
newnode->_next = _head;
_head->_prev = newnode;*/
insert(end(), x);
}
void pop_back()
{
erase(--end());
}
void push_front(const T& x)
{
insert(begin(), x);
}
void pop_front()
{
erase(begin());
}
void insert(iterator pos, const T& x)
{
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* newnode = new Node(x);
//prev newnode cur
prev->_next = newnode;
newnode->_prev = prev;
newnode->_next = cur;
cur->_prev = newnode;
}
void erase(iterator pos)
{
assert(pos != end());
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* next = cur->_next;
delete cur;
prev->_next = next;
next->_prev = prev;
}
private:
Node* _head;
};
void test_list1()
{
list<int> ls;
ls.push_back(1);
ls.push_back(2);
ls.push_back(3);
ls.push_back(4);
list<int>::iterator it = ls.begin();
while (it != ls.end())
{
cout << *it << " ";
++it;
}
cout << endl;
}
struct Date
{
int _year = 0;
int _month = 1;
int _day = 1;
};
void test_list2()
{
list<Date> ls;
ls.push_back(Date());
ls.push_back(Date());
list<Date>::iterator it = ls.begin();
while (it != ls.end())
{
cout << it->_year << "-" << it->_month << "-" << it->_day << endl;
++it;
}
cout << endl;
}
void print_list(const list<int>& lt)
{
list<int>::const_iterator it = lt.begin();
while (it != lt.end())
{
cout << *it << " ";
++it;
}
cout << endl;
}
void test_list3()
{
list<int> ls;
ls.push_back(1);
ls.push_back(2);
ls.push_back(3);
ls.push_back(4);
ls.insert(ls.begin(), 0);
ls.push_front(-1);
print_list(ls);
ls.pop_front();
ls.pop_back();
print_list(ls);
ls.clear();
ls.push_back(1);
print_list(ls);
}
void test_list4()
{
list<int> lst1;
lst1.push_back(1);
lst1.push_back(2);
lst1.push_back(3);
lst1.push_back(4);
list<int> lst2(lst1);
print_list(lst2);
list<int> lst3;
lst3.push_back(10);
lst3.push_back(20);
lst3.push_back(30);
lst3.push_back(40);
lst1 = lst3;
print_list(lst1);
}
}
2.list.cpp
#include"list.h"
int main()
{
wzyl::test_list1();
//wzyl::test_list2();
//wzyl::test_list3();
//wzyl::test_list4();
return 0;
}
标签:node,head,iterator,STL,list,C++,next,prev
From: https://blog.csdn.net/w200514/article/details/143609630