文章目录
一、list的介绍及使用
1.list的介绍
c++中list为双向带头循环列表
2.list的使用
2.1 构造
cpp
#include <iostream>
using namespace std;
#include <list>
#include <vector>
// list的构造
void TestList1()
{
list<int> l1; // 构造空的l1
list<int> l2(4, 100); // l2中放4个值为100的元素
list<int> l3(l2.begin(), l2.end()); // 用l2的[begin(), end()）左闭右开的区间构造l3
list<int> l4(l3); // 用l3拷贝构造l4
// 以数组为迭代器区间构造l5
int array[] = { 16,2,77,29 };
list<int> l5(array, array + sizeof(array) / sizeof(int));
// 列表格式初始化C++11
list<int> l6{ 1,2,3,4,5 };
// 用迭代器方式打印l5中的元素
list<int>::iterator it = l5.begin();
while (it != l5.end())
{
cout << *it << " ";
++it;
}
cout << endl;
// C++11范围for的方式遍历
for (auto& e : l5)
cout << e << " ";
cout << endl;
}2.2 迭代器
注意：list的迭代器不支持+，- 操作符
注意：
-
begin与end为正向迭代器，对迭代器执行++操作，迭代器向后移动
-
rbegin(end)与rend(begin)为反向迭代器，对迭代器执行++操作，迭代器向前移动
cpp
// list迭代器的使用
// 注意：遍历链表只能用迭代器和范围for
void PrintList(const list<int>& l)
{
// 注意这里调用的是list的 begin() const，返回list的const_iterator对象
for (list<int>::const_iterator it = l.begin(); it != l.end(); ++it)
{
cout << *it << " ";
// *it = 10; 编译不通过
}
cout << endl;
}
void TestList2()
{
int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
list<int> l(array, array + sizeof(array) / sizeof(array[0]));
// 使用正向迭代器正向list中的元素
// list<int>::iterator it = l.begin(); // C++98中语法
auto it = l.begin(); // C++11之后推荐写法
while (it != l.end())
{
cout << *it << " ";
++it;
}
cout << endl;
// 使用反向迭代器逆向打印list中的元素
// list<int>::reverse_iterator rit = l.rbegin();
auto rit = l.rbegin();
while (rit != l.rend())
{
cout << *rit << " ";
++rit;
}
cout << endl;
}2.3 空间
2.4 节点访问
2.5 修改
cpp
// list插入和删除
// push_back/pop_back/push_front/pop_front
void TestList3()
{
int array[] = { 1, 2, 3 };
list<int> L(array, array + sizeof(array) / sizeof(array[0]));
// 在list的尾部插入4，头部插入0
L.push_back(4);
L.push_front(0);
PrintList(L);
// 删除list尾部节点和头部节点
L.pop_back();
L.pop_front();
PrintList(L);
}
// insert /erase
void TestList4()
{
int array1[] = { 1, 2, 3 };
list<int> L(array1, array1 + sizeof(array1) / sizeof(array1[0]));
// 获取链表中第二个节点
auto pos = ++L.begin();
cout << *pos << endl;
// 在pos前插入值为4的元素
L.insert(pos, 4);
PrintList(L);
// 在pos前插入5个值为5的元素
L.insert(pos, 5, 5);
PrintList(L);
// 在pos前插入[v.begin(), v.end)区间中的元素
vector<int> v{ 7, 8, 9 };
L.insert(pos, v.begin(), v.end());
PrintList(L);
// 删除pos位置上的元素
L.erase(pos);
PrintList(L);
// 删除list中[begin, end)区间中的元素，即删除list中的所有元素
L.erase(L.begin(), L.end());
PrintList(L);
}二、迭代器失效
可将迭代器暂时理解成类似于指针，迭代器失效即迭代器所指向的节点的无效，即该节点被删除了。
因为list的底层结构为带头结点的双向循环链表，因此在list中进行插入时是不会导致list的迭代器失效的 ， 只有在删除时才会失效，并且失效的只是指向被删除节点的迭代器，其他迭代器不会受到影响。
cpp
void TestListIterator1()
{
int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
list<int> l(array, array + sizeof(array) / sizeof(array[0]));
auto it = l.begin();
while (it != l.end())
{
// erase()函数执行后，it所指向的节点已被删除，因此it无效，在下一次使用it时，必须先给其赋值
l.erase(it);
++it;
}
}
// 改正
void TestListIterator()
{
int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
list<int> l(array, array + sizeof(array) / sizeof(array[0]));
auto it = l.begin();
while (it != l.end())
{
l.erase(it++); // it = l.erase(it);
}
}三、list的模拟实现
3.1 基本结构
cpp
template<class T>
struct list_node
{
list_node(const T& date = T())
:_date(date)
,_prev(nullptr)
,_next(nullptr)
{}
T _date;
list_node<T>* _prev;
list_node<T>* _next;
};
template<class T>
class list
{
typedef list_node<T> Node;
private:
Node* _head;
size_t _size;
};3.2 构造和析构
cpp
void empty_init()
{
_head = new Node;
_head->_prev = _head;
_head->_next = _head;
_size = 0;
}
list()
{
empty_init();
}
list(initializer_list<T> il)
{
empty_init();
for (auto& e : il)
{
push_back(e);
}
}
list(const list<T>& l1)
{
empty_init();
for (auto& e : l1)
{
push_back(e);
}
}
~list()
{
clear();
delete _head;
_head = nullptr;
}3.3 迭代器
由于list的储存空间不是连续的，所以我们要单独实现++/--等操作，所以我们直接放在一个类中去实现它
cpp
template<class T>
struct list_iterator
{
typedef list_node<T> Node;
typedef list_iterator<T> Self;
Node* _node;
list_iterator(Node* node)
{
_node = node;
}
T& operator*()
{
return _node->_date;
}
T* operator->()
{
return &_node->_date;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self operator--(int)
{
Self tmp(*this);
_node = _node->_prev;
return tmp;
}
bool operator!=(const Self& s) const
{
return _node != s._node;
}
bool operator==(const Self& s) const
{
return _node == s._node;
}
};但是这样写太过麻烦，我们看库里面是如何实现的
cpp
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->_date;
}
Ptr operator->()
{
return &_node->_date;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self operator--(int)
{
Self tmp(*this);
_node = _node->_prev;
return tmp;
}
bool operator!=(const Self& s) const
{
return _node != s._node;
}
bool operator==(const Self& s) const
{
return _node == s._node;
}
};在list里面这样写，就方便了很多
cpp
typedef list_iterator<T,T&,T*> iterator;
typedef list_iterator<T,const T&, const T*> const_iterator;
iterator begin()
{
return _head->_next;
}
iterator end()
{
return _head;
}
const_iterator begin() const
{
return _head->_next;
}
const_iterator end() const
{
return _head;
}3.4 空间
cpp
size_t size() const
{
return _size;
}
bool empty() const
{
return _size == 0;
}3.5 修改
cpp
list<T>& operator=(list<T> l1)
{
swap(l1);
return *this;
}
void swap(list<T> tmp)
{
std::swap(_head, tmp._head);
std::swap(_size, tmp._size);
}
void push_back(const T& x)
{
/*Node* newnode = new Node(x);
Node* tail = _head->_prev;
tail->_next = newnode;
newnode->_prev = tail;
newnode->_next = _head;
_head->_prev = newnode;
++_size;*/
insert(end(), x);
}
void push_front(const T& x)
{
insert(begin(), x);
}
iterator insert(iterator pos, const T& x)
{
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* newnode = new Node(x);
//prev newnode cur
newnode->_next = cur;
newnode->_prev = prev;
prev->_next = newnode;
cur->_prev = newnode;
++_size;
return newnode;
}
void pop_back()
{
erase(--end());
}
void pop_front()
{
erase(begin());
}
iterator erase(iterator pos)
{
assert(pos != end());
Node* prev = pos._node->_prev;
Node* next = pos._node->_next;
prev->_next = next;
next->_prev = prev;
delete pos._node;
pos._node = nullptr;
--_size;
return next;
}
void clear()
{
auto it = begin();
while (it != end())
{
it = erase(it);
}
}3.6 源代码
list.h
cpp
#pragma once
#include <iostream>
#include <assert.h>
#include <list>
using namespace std;
namespace mihayou
{
template<class T>
struct list_node
{
list_node(const T& date = T())
:_date(date)
,_prev(nullptr)
,_next(nullptr)
{}
T _date;
list_node<T>* _prev;
list_node<T>* _next;
};
/*template<class T>
struct list_iterator
{
typedef list_node<T> Node;
typedef list_iterator<T> Self;
Node* _node;
list_iterator(Node* node)
{
_node = node;
}
T& operator*()
{
return _node->_date;
}
T* operator->()
{
return &_node->_date;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self operator--(int)
{
Self tmp(*this);
_node = _node->_prev;
return tmp;
}
bool operator!=(const Self& s) const
{
return _node != s._node;
}
bool operator==(const Self& s) const
{
return _node == s._node;
}
};*/
/*template<class T>
struct list_const_iterator
{
typedef list_node<T> Node;
typedef list_const_iterator<T> Self;
Node* _node;
list_const_iterator(Node* node)
{
_node = node;
}
const T& operator*()
{
return _node->_date;
}
const T* operator->()
{
return &_node->_date;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self operator--(int)
{
Self tmp(*this);
_node = _node->_prev;
return tmp;
}
bool operator!=(const Self& s) const
{
return _node != s._node;
}
bool operator==(const Self& s) const
{
return _node == s._node;
}
};*/
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->_date;
}
Ptr operator->()
{
return &_node->_date;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self operator--(int)
{
Self tmp(*this);
_node = _node->_prev;
return tmp;
}
bool operator!=(const Self& s) const
{
return _node != s._node;
}
bool operator==(const Self& s) const
{
return _node == s._node;
}
};
template<class T>
class list
{
typedef list_node<T> Node;
public:
/*typedef list_iterator<T> iterator;
typedef list_const_iterator<T> const_iterator;*/
typedef list_iterator<T,T&,T*> iterator;
typedef list_iterator<T,const T&, const T*> const_iterator;
iterator begin()
{
return _head->_next;
}
iterator end()
{
return _head;
}
const_iterator begin() const
{
return _head->_next;
}
const_iterator end() const
{
return _head;
}
void empty_init()
{
_head = new Node;
_head->_prev = _head;
_head->_next = _head;
_size = 0;
}
list()
{
empty_init();
}
list(initializer_list<T> il)
{
empty_init();
for (auto& e : il)
{
push_back(e);
}
}
list(const list<T>& l1)
{
empty_init();
for (auto& e : l1)
{
push_back(e);
}
}
list<T>& operator=(list<T> l1)
{
swap(l1);
return *this;
}
void swap(list<T> tmp)
{
std::swap(_head, tmp._head);
std::swap(_size, tmp._size);
}
void push_back(const T& x)
{
/*Node* newnode = new Node(x);
Node* tail = _head->_prev;
tail->_next = newnode;
newnode->_prev = tail;
newnode->_next = _head;
_head->_prev = newnode;
++_size;*/
insert(end(), x);
}
void push_front(const T& x)
{
insert(begin(), x);
}
iterator insert(iterator pos, const T& x)
{
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* newnode = new Node(x);
//prev newnode cur
newnode->_next = cur;
newnode->_prev = prev;
prev->_next = newnode;
cur->_prev = newnode;
++_size;
return newnode;
}
void pop_back()
{
erase(--end());
}
void pop_front()
{
erase(begin());
}
iterator erase(iterator pos)
{
assert(pos != end());
Node* prev = pos._node->_prev;
Node* next = pos._node->_next;
prev->_next = next;
next->_prev = prev;
delete pos._node;
pos._node = nullptr;
--_size;
return next;
}
size_t size() const
{
return _size;
}
bool empty() const
{
return _size == 0;
}
~list()
{
clear();
delete _head;
_head = nullptr;
}
void clear()
{
auto it = begin();
while (it != end())
{
it = erase(it);
}
}
private:
Node* _head;
size_t _size;
};
//按需实例化
template<class Container>
void print_container(const Container& con)
{
//const iterator -> 迭代器本身不能修改
//const_iterator -> 指向内容不能改变
//typename Container::const_iterator it = con.begin();
auto it = con.begin();
while (it != con.end())
{
//*it += 10;
cout << *it << " ";
it++;
}
cout << endl;
/*for (auto e : con)
{
cout << e << " ";
}
cout << endl;*/
}
}list.cpp
cpp
#include "list.h"
namespace mihayou
{
struct AA
{
int _a1 = 1;
int _a2 = 1;
};
void test01()
{
list<int> v1;
v1.push_back(1);
v1.push_back(2);
v1.push_back(3);
v1.push_back(4);
v1.push_front(6);
v1.pop_back();
v1.pop_front();
auto itt = v1.begin();
int k = 1;
while (k--)
{
++itt;
}
v1.erase(itt);
list<int>::iterator it = v1.begin();
while (it != v1.end())
{
*it += 10;
cout << *it << " ";
++it;
}
cout << endl;
print_container(v1);
list<AA> aa;
aa.push_back(AA());
aa.push_back(AA());
aa.push_back(AA());
aa.push_back(AA());
list<AA>::iterator ita = aa.begin();
while (ita != aa.end())
{
cout << ita->_a1 << " " << ita->_a2 << " ";
//cout << ita.operator->()->_a1 << " " << ita.operator->()->_a2 << " ";
++ita;
}
cout << endl;
}
void test02()
{
list<int> l1;
l1.push_back(1);
l1.push_back(2);
l1.push_back(3);
l1.push_back(4);
//insert以后迭代器不失效
list<int>::iterator it = l1.begin();
l1.insert(it,10);
*it += 10;
print_container(l1);
//erase以后迭代器不失效
auto itt = l1.begin();
while (itt != l1.end())
{
if (*itt % 2 == 0)
{
itt = l1.erase(itt);
}
else
{
itt++;
}
}
print_container(l1);
}
void test03()
{
list<int> l1;
l1.push_back(1);
l1.push_back(2);
l1.push_back(3);
l1.push_back(4);
print_container(l1);
list<int> l2(l1);
print_container(l2);
list<int> l3;
l3 = l1;
print_container(l3);
}
void fun(const list<int>& lt)
{
print_container(lt);
}
void test04()
{
list<int> l0({ 1,2,3,4 });
//隐式类型转换
list<int> l1 = { 1,2,3,4 };
print_container(l1);
const list<int>& l2 = { 1,2,3,4 };
fun(l1);
fun({ 1,2,3,4 });
//auto l1 = { 1,2,3,4 };
/*initializer_list<int> l1 = { 1,2,3,4 };
cout << typeid(l1).name() << endl;
cout << sizeof(l1) << endl;*/
}
}
int main()
{
mihayou::test01();
return 0;
}四、list与vector的对比
