list的细节
list的细节之一就是其迭代器没有使用指针了，因为指针是无法达到迭代器的效果的，再补充下迭代器的类型，迭代器分为单向，双向，随机迭代器，单向迭代器的容器有forward_list，unordered_map等，单向迭代器只支持++，双向迭代器有list,map，双向迭代器支持++与–，随机迭代器有string，vector，deque支持++，–，+，-，迭代器的名字决定了其类型，list本身是有sort函数的，但是效率过低，不如将他粘贴到vector进行sort在粘贴回来，后续有代码证明。list也存在迭代器失效问题，list的insert相比于vector是没有失效问题的，因为list的insert不存在扩容问题，基本所有的erase都有迭代器失效问题，所以每个erase都会返回删除下一个位置的迭代器，string也是有的，只是string更习惯用[]而不是迭代器进行访问。
头文件
#pragma once
#include<assert.h>
namespace prime
{
template<class T>
struct list_node
{
list_node* _next;
list_node* _prev;
T _data;
list_node(const T& x = T())
:_next(nullptr)
, _prev(nullptr)
, _data(x)
{}
};
//这里是封装了iterator类，因为list的原生指针无法作为迭代器
// typedef list_iterator<T, T&, T*> iterator;三个模版参数，是为了后面的const做铺垫
// 如果需要const迭代器，我们是没办法完成的，所以这里封装一个const_iterator，由于普通ite与const的区别
// 就只有*上，所以就通过添加参数来进行合并
// typedef list_iterator<T, const T&, const T*> const_iterator;
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)//因为tmp会销毁，所以不能传引用
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
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->_data;
}
Self& operator++()
{
_node = _node->_next;
return *this;
}
Self operator++(int)
{
Self tmp(*this);
_node = _node->_next;
return tmp;
}
Self& operator--()
{
_node = _node->_prev;
return *this;
}
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, T&, T*> iterator;
//typedef list_const_iterator<T> const_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);
}
//这里单独封装一个初始化函数不选择用初始化列表进行初始化，是因为后续需要额外创建链表时需要初始化
//初始化头节点需要创建Node对象并设置其_next和_prev指针指向自身。
//这类多步操作无法直接在构造函数的初始化列表中完成（初始化列表仅支持表达式，不支持语句）
void empty_init()
{
_head = new Node;
_head->_next = _head;
_head->_prev = _head;
_size = 0;
}
list()
{
empty_init();
}
list(initializer_list<T> il)
{
empty_init();
for (auto& e : il)
{
push_back(e);
}
}
// lt2(lt1)
//list(const list<T>& lt)
list(list<T>& lt)
{
empty_init();
for (auto& e : lt)
{
push_back(e);
}
}
void swap(list<T>& lt)
{
std::swap(_head, lt._head);
std::swap(_size, lt._size);
}
// lt1 = lt3
list<T>& operator=(list<T> lt)
{
swap(lt);
return *this;
}
~list()
{
clear();
delete _head;
_head = nullptr;
}
void clear()
{
auto it = begin();
while (it != end())
{
it = erase(it);
}
}
size_t size()
{
return _size;
}
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 push_front(const T& x)
{
insert(begin(), x);
}
void pop_back()
{
erase(--end());
}
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;
++_size;
}
iterator erase(iterator pos)
{
assert(pos != end());
Node* cur = pos._node;
Node* prev = cur->_prev;
Node* next = cur->_next;
prev->_next = next;
next->_prev = prev;
delete cur;
--_size;
//return iterator(next);
return next;
}
private:
Node* _head;
size_t _size;
};
void test_list1()
{
list<int> lt;
lt.push_back(1);
lt.push_back(2);
lt.push_back(3);
lt.push_back(4);
list<int>::iterator it = lt.begin();
while (it != lt.end())
{
*it += 10;
cout << *it << " ";
++it;
}
cout << endl;
lt.push_front(1);
lt.push_front(2);
lt.push_front(3);
lt.push_front(4);
for (auto e : lt)
{
cout << e << " ";
}
cout << endl;
lt.pop_back();
lt.pop_back();
lt.pop_front();
lt.pop_front();
for (auto e : lt)
{
cout << e << " ";
}
cout << endl;
}
void test_list2()
{
list<int> lt;
lt.push_back(1);
lt.push_back(2);
lt.push_back(3);
lt.push_back(4);
list<int>::iterator it = lt.begin();
while (it != lt.end())
{
if (*it % 2 == 0)
{
it = lt.erase(it);
}
else
{
++it;
}
}
for (auto e : lt)
{
cout << e << " ";
}
cout << endl;
}
// const T* p1;
// T* const p2;
void print(const list<int>& lt)
{
// const迭代器的要求不是本身不能修改，而是指向的内容不能修改
//const list<int>::iterator it = lt.begin();
list<int>::const_iterator it = lt.begin();
while (it != lt.end())
{
// *it = 10;
cout << *it << " ";
++it;
}
cout << endl;
}
void test_list3()
{
list<int> lt1;
lt1.push_back(1);
lt1.push_back(2);
lt1.push_back(3);
lt1.push_back(4);
for (auto e : lt1)
{
cout << e << " ";
}
cout << endl;
list<int> lt2(lt1);
for (auto e : lt2)
{
cout << e << " ";
}
cout << endl;
list<int> lt3 = { 1,2,3,4,5,6 };
lt1 = lt3;
for (auto e : lt1)
{
cout << e << " ";
}
cout << endl;
}
struct AA
{
int _a1;
int _a2;
AA(int a1 = 1, int a2 = 1)
:_a1(a1)
, _a2(a2)
{}
};
void test_list4()
{
//AA aa1 = { 1,1 };
vector<AA> v1;
v1.push_back({ 1,1 });
v1.push_back({ 2,2 });
v1.push_back({ 3,3 });
vector<AA>::iterator it1 = v1.begin();
while (it1 != v1.end())
{
cout << it1->_a1 << ":" << it1->_a2 << endl;
++it1;
}
cout << endl;
list<AA> lt1;
lt1.push_back({ 1,1 });
lt1.push_back({ 2,2 });
lt1.push_back({ 3,3 });
list<AA>::iterator lit1 = lt1.begin();
while (lit1 != lt1.end())
{
//cout << (*lit1)._a1 <<":"<< (*lit1)._a2 << endl;
// 特殊处理，省略了一个->,为了可读性
cout << lit1->_a1 << ":" << lit1->_a2 << endl;
cout << lit1.operator->()->_a1 << ":" << lit1.operator->()->_a2 << endl;
++lit1;
}
cout << endl;
}
}
源码
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<list>
#include<vector>
#include<algorithm>
using namespace std;
//int main()
//{
// // 21:05
// list<int> lt1 = {1,2,2,2,3,3,4,2,3,5,6};
// for (auto e : lt1)
// {
// cout << e << " ";
// }
// cout << endl;
// sort(lt1.begin(), lt1.end());
//
// /*lt1.sort();
// lt1.unique();*/
// lt1.remove(2);
// for (auto e : lt1)
// {
// cout << e << " ";
// }
// cout << endl;
//
// return 0;
//}
void test_op1()
{
srand(time(0));
const int N = 1000000;
list<int> lt1;
vector<int> v;
for (int i = 0; i < N; ++i)
{
auto e = rand() + i;
lt1.push_back(e);
v.push_back(e);
}
int begin1 = clock();
// 排序
sort(v.begin(), v.end());
int end1 = clock();
int begin2 = clock();
lt1.sort();
int end2 = clock();
printf("vector sort:%d\n", end1 - begin1);
printf("list sort:%d\n", end2 - begin2);
}
void test_op2()
{
srand(time(0));
const int N = 1000000;
list<int> lt1;
list<int> lt2;
for (int i = 0; i < N; ++i)
{
auto e = rand() + i;
lt1.push_back(e);
lt2.push_back(e);
}
int begin1 = clock();
// 拷贝vector
vector<int> v(lt2.begin(), lt2.end());
// 排序
sort(v.begin(), v.end());
// 拷贝回lt2
lt2.assign(v.begin(), v.end());
int end1 = clock();
int begin2 = clock();
lt1.sort();
int end2 = clock();
printf("list copy vector sort copy list sort:%d\n", end1 - begin1);
printf("list sort:%d\n", end2 - begin2);
}
void test_list1()
{
// 一个链表的节点移动到另一个链表
std::list<int> lt1 = { 1, 2, 3, 4, 5 };
std::list<int> lt2 = { 10, 20, 30, 40 };
for (auto e : lt1)
{
cout << e << " ";
}
cout << endl;
for (auto e : lt2)
{
cout << e << " ";
}
cout << endl;
lt1.splice(lt1.begin(), lt2);
for (auto e : lt1)
{
cout << e << " ";
}
cout << endl;
for (auto e : lt2)
{
cout << e << " ";
}
cout << endl;
// 一个链表中节点调整顺序
std::list<int> lt3 = { 1, 2, 3, 4, 5 };
int x;
cin >> x;
auto it = find(lt3.begin(), lt3.end(), x);
if (it != lt3.end())
{
lt3.splice(lt3.begin(), lt3, it);
}
for (auto e : lt3)
{
cout << e << " ";
}
cout << endl;
}
#include"List.h"
int main()
{
prime::test_list4();
return 0;
}