list类的详细讲解

1. list的介绍及使用

1.1 list的介绍

1.2 list的使用

1.2.1 list的构造

#define _CRT_SECURE_NO_WARNINGS#include <iostream>
using namespace std;
#include <list>
#include <vector>// list的构造
void TestList1()
{list<int> l1;                         // 构造空的l1list<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l3list<int> l4(l3);                    // 用l3拷贝构造l4// 以数组为迭代器区间构造l5int array[] = { 16,2,77,29 };list<int> l5(array, array + sizeof(array) / sizeof(int));// 列表格式初始化C++11list<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;
}

1.2.2 list iterator的使用

// 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;
}

1.2.3 list capacity

1.2.4 list element access

1.2.5 list modifiers

// 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0L.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);
}
// resize/swap/clear
void TestList5()
{// 用数组来构造listint array1[] = { 1, 2, 3 };list<int> l1(array1, array1 + sizeof(array1) / sizeof(array1[0]));PrintList(l1);// 交换l1和l2中的元素list<int> l2;l1.swap(l2);PrintList(l1);PrintList(l2);// 将l2中的元素清空l2.clear();cout << l2.size() << endl;
}

1.2.6 list的迭代器失效

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);}
}

2. list的模拟实现

2.1 模拟实现list

#pragma once
#include <assert.h>
#include <iostream>namespace xyl
{template<class T>//list节点类struct ListNode{ListNode(const T& val = T()):_pPrev(nullptr), _pNext(nullptr),_val(val){}ListNode<T>* _pPrev;ListNode<T>* _pNext;T _val;};//List迭代器类template<class T,class Ref,class Ptr>struct ListIterator{typedef ListNode<T>* PNode;typedef ListIterator<T, Ref, Ptr> Self;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++(){_pNode = _pNode->_pNext;return *this;}Self operator++(int){Self tmp(*this);_pNode = _pNode->_pNext;return tmp;}Self& operator--(){_pNode = _pNode->_pPrev;return *this;}Self& operator--(int){Self tmp(*this);_pNode = _pNode->_pPrev;return tmp;}bool operator==(const Self& l){return _pNode == l._pNode;}bool operator!=(const Self& l){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:void init_empty(){_head = new Node;_head->_pPrev = _head;_head->_pNext = _head;size = 0;}list(){init_empty();}list(int n, const T& val = T()){init_empty();for (int i = 0;i < n;i++){push_back(val);}}template <class Iterator>list(Iterator first, Iterator last){init_empty();while (first != last){push_back(*first);first++;}}list(const list<T>& l){init_empty();const_iterator it = l.begin();while (it != l.end()){push_back(*it);it++;}}~list(){clean();delete _head;_head = nullptr;}void clean(){iterator it = begin();while (it != end()){it=erase(it);}_head->_pNext = _head;_head->_pPrev = _head;}list<T>& operator=(const list<T>& l){list<T> tmp(l);swap(tmp);return *this;}size_t _size(){return size;}bool empty(){return size == 0;}T& front(){return _head->_pNext->_val;}T& back(){return _head->_pPrev->_val;}const T& front() const{return _head->_pNext->_val;}const T& back() const{return _head->_pPrev->_val;}void push_back(const T& val){/*PNode cur= new Node(val);PNode tail = _head->_pPrev;cur->_pPrev = tail;cur->_pNext = _head;tail->_pNext = cur;_head->_pPrev = cur;size++;*/insert(end(), val);}void push_front(const T& val){insert(begin(), val);}void pop_back(){erase(--end());}void pop_front(){erase(begin());}iterator insert(iterator pos, const T& val){PNode newnode = new Node(val);PNode cur = pos._pNode;PNode prev = cur->_pPrev;prev->_pNext = newnode;newnode->_pPrev = prev;newnode->_pNext = cur;cur->_pPrev = newnode;size++;return iterator(newnode);}iterator erase(iterator pos){//找到删除节点PNode del = pos._pNode;//存储删除节点的下一位当返回值PNode tmp = del->_pNext;PNode next = del->_pNext;PNode prev = del->_pPrev;prev->_pNext = next;next->_pPrev = prev;delete del;size--;return iterator(tmp);}iterator begin() {return (_head->_pNext);}iterator end() {return (_head);}const_iterator begin() const{return (_head->_pNext);}const_iterator end() const{return (_head);}void swap(list<T>& l){std::swap(_head, l._head);std::swap(size, l.size);}PNode _head;size_t size;};
}

#include <iostream>#include "list.h"using namespace std;void test_list1()
{xyl::list<int> list1;list1.push_back(1);list1.push_back(2);list1.push_back(3);list1.push_back(4);xyl::list<int>:: iterator it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;cout << list1.size;cout << endl;xyl::list<int> list2(10,1);xyl::list<int>::iterator it2 = list2.begin();while (it2 != list2.end()){cout << (*it2) << ' ';++it2;}cout << endl;}void test_list2()
{xyl::list<int> list1;list1.push_back(1);list1.push_back(2);list1.push_back(3);list1.push_back(4);xyl::list<int>::iterator it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;xyl::list<int> list2(++list1.begin(),list1.end());xyl::list<int>::iterator it2 = list2.begin();while (it2 != list2.end()){cout << (*it2) << ' ';++it2;}cout << endl;xyl::list<int> list3(list2);xyl::list<int>::iterator it3 = list3.begin();while (it3 != list3.end()){cout << (*it3) << ' ';++it3;}cout << endl;
}void test_list3()
{xyl::list<int> list1;list1.push_back(1);list1.push_back(2);list1.push_back(3);list1.push_back(4);xyl::list<int>::iterator it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;xyl::list<int> list2;list2 = list1;xyl::list<int>::iterator it2 = list2.begin();while (it2 != list2.end()){cout << (*it2) << ' ';++it2;}cout << endl;cout << list2.front() << endl;cout << list2.back() << endl;
}void test_list4()
{xyl::list<int> list1;list1.push_back(1);list1.push_back(2);list1.push_back(3);list1.push_back(4);list1.erase(list1.begin());xyl::list<int>::iterator it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}list1.clean();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}}void test_list5()
{xyl::list<int> list1;list1.push_back(1);list1.push_back(2);list1.push_back(3);list1.push_back(4);list1.insert(list1.begin(), 3);xyl::list<int>::iterator it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;list1.pop_back();it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;list1.pop_front();it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;list1.push_front(5);it1 = list1.begin();while (it1 != list1.end()){cout << (*it1) << ' ';++it1;}cout << endl;
}int main()
{test_list5();return 0;
}

2.2 list的反向迭代器

template<class Iterator>
class ReverseListIterator
{// 注意：此处typename的作用是明确告诉编译器，Ref是Iterator类中的类型，而不是静态成员变量// 否则编译器编译时就不知道Ref是Iterator中的类型还是静态成员变量// 因为静态成员变量也是按照 类名::静态成员变量名 的方式访问的
public:typedef typename Iterator::Ref Ref;typedef typename Iterator::Ptr Ptr;typedef ReverseListIterator<Iterator> Self;
public://// 构造ReverseListIterator(Iterator it) : _it(it) {}//// 具有指针类似行为Ref operator*() {Iterator temp(_it);--temp;return *temp;}Ptr operator->() { return &(operator*()); }//// 迭代器支持移动Self& operator++() {--_it;return *this;}Self operator++(int) {Self temp(*this);--_it;return temp;}Self& operator--() {++_it;return *this;}Self operator--(int){Self temp(*this);++_it;return temp;}//// 迭代器支持比较bool operator!=(const Self& l)const { return _it != l._it; }bool operator==(const Self& l)const { return _it != l._it; }Iterator _it;
};

3. list与vector的对比