[C++笔记]list

//stl的list是带头双向循环链表
#pragma once
#include <iostream>
#include <list>
#include<assert.h>
using namespace std;

namespace MyList{
	template<class T>
	struct list_node {
		list_node<T>* _next;
		list_node<T>* _prev;
		T _data;

		list_node(const T& x = T())//匿名对象作为缺省值。不可以用0作为缺省值，因为T未必是int类型。(若不设缺省值，没有默认构造函数可能编译不通过)
			:_next(nullptr)
			,_prev(nullptr)
			,_data(x)
		{}
	};

	//迭代器(含const迭代器)
	//迭代器要么直接是原生指针，要么是自定义类型对原生指针的封装--模拟指针的行为。
	template<class T,class Ref,class Ptr>//Ptr是给 -> 运算符重载的返回用的
	struct __list_iterator{
		typedef list_node<T> node;
		typedef __list_iterator<T,Ref,Ptr> self;
		node* _node;

		__list_iterator(node* n)
			:_node(n)
		{}

		Ref operator*() {//通过模板参数控制是否为const迭代器：普通迭代器相比const迭代器，只有这里的返回值需要不一样，const的传const T& ，普通的传T&
			return _node->_data;
		}

		Ptr operator->() {
			return &_node->_data;
		}

		//前置++
		//__list_iterator<T>& operator++() {
		self& operator++(){//迭代器++返回迭代器
			_node = _node->_next;
			return *this;
		}
		//后置++
		self operator++(int) {
			self tmp(*this);
			_node = _node->_next;
			return tmp;
		}

		//前置--
		self& operator--() {
			_node = _node->_prev;
			return *this;
		}
		//后置--
		self operator--(int) {
			self tmp(*this);
			_node = _node->_prev;
			return tmp;
		}

		bool operator!=(const self& s) {
			return _node != s._node;
		}
		bool operator==(const self& s) {
			return _node == s._node;
		}
	};

	template<class T>
	class list {
		typedef list_node<T> node;
	public:
		//typedef __list_iterator<T> iterator;//迭代器对标指针：T*
		//typedef const iterator const_iterator;//这样写会相当于T* const，迭代器本身不能修改了。而需要的是仅内容不可修改的const T*
		typedef __list_iterator<T,T&,T*> iterator;
		typedef __list_iterator<T,const T&,const T*> const_iterator;
		
		iterator begin() {
			return iterator(_head->_next);
		}
		const_iterator begin() const {
			return const_iterator(_head->_next);
		}

		iterator end() {
			return iterator(_head);
		}
		const_iterator end() const {
			return const_iterator(_head);
		}

		void empty_init() {
			//_head = new list_node<T>;//加模板参数才是类型，否则就是类名
			_head = new node;//↑使用typedef简化
			_head->_next = _head;
			_head->_prev = _head;
		}

		list() {
			empty_init();
		}

		template<class Iterator>
		list(Iterator first, Iterator last) {
			empty_init();
			while (first != last) {
				push_back(*first);
				++first;
			}
		}

		void swap(list<T>& tmp) {
			std::swap(_head, tmp._head);
		}

		list(const list<T>& lt) {
			empty_init();
			list<T> tmp(lt.begin(), lt.end());
			swap(tmp);
		}

		list<T>& operator=(list<T> lt) {
			swap(lt);
			return *this;
		}

		~list() {
			//全清，包括头节点
			clear();
			delete _head;
			_head = nullptr;
		}

		void clear() {
			//不清头节点
			iterator it = begin();
			while (it!=end()){
				it = erase(it);
			}
		}

		//pos前插入
		void insert(iterator pos,const T& x) {
			node* cur = pos._node;
			node* prev = cur->_prev;
			node* new_node = new node(x);
			prev->_next = new_node;
			new_node->_prev = prev;
			new_node->_next = cur;
			cur->_prev = new_node;
		}

		iterator erase(iterator pos) {
			assert(pos != end());//哨兵位头节点不能erase
			node* prev = pos._node->_prev;
			node* next = pos._node->_next;
			prev->_next = next;
			next->_prev = prev;
			delete pos._node;
			return iterator(next);
		}

		void push_back(const T& x) {
			insert(end(), x);
		}
		void push_front(const T& x) {
			insert(begin(), x);
		}
		void pop_back() {
			erase(--end());
		}
		void pop_front() {
			erase(begin());
		}

	private:
		//list_node<T>* _head;//这里模板参数<T>理论上可以不加，但最好还是养成加上的习惯，因为不加的话编译器可能会报错
		node* _head;//↑使用typedef简化
	};

	void print_list(const list<int>& lt) {
		list<int>::const_iterator it = lt.begin();
		while (it != lt.end()){
			//(*it) *= 2;//const测试用
			cout << *it << " ";
			++it;
		}
		cout << endl;
	}

	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) *= 2;
			cout << *it << " ";
			++it;
		}
		cout << endl;

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;

		print_list(lt);
	}

	struct AA {
		int _a1;
		int _a2;
		AA(int a1 = 0,int a2 = 0)
			:_a1(a1)
			,_a2(a2)
		{}
	};

	void test_list2() {
		list<AA> lt;
		lt.push_back(AA(1, 1));
		lt.push_back(AA(2, 2));
		lt.push_back(AA(3, 3));

		list<AA>::iterator it = lt.begin();
		while (it != lt.end()) {
			cout << it->_a1 << ":" << it->_a2 << endl;//原本应当是 it->->_a1，但为增强可读性，用法上省略一个 ->
			++it;
		}
		cout << endl;
	}

	void test_list3() {
		list<int> lt;
		lt.push_back(1);
		lt.push_back(2);
		lt.push_back(3);
		lt.push_back(4);

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;

		auto pos = lt.begin();
		++pos;
		lt.insert(pos, 114);

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;

		lt.push_back(514);
		lt.push_front(1919);

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;
	}

	void test_list4() {
		list<int> lt;
		lt.push_back(1);
		lt.push_back(2);
		lt.push_back(3);
		lt.push_back(4);

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;

		lt.clear();

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;

		lt.push_back(11);
		lt.push_back(12);
		lt.push_back(13);
		lt.push_back(14);

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;
	}

	void test_list5() {
		list<int> lt;
		lt.push_back(1);
		lt.push_back(2);
		lt.push_back(3);
		lt.push_back(4);
		lt.push_back(5);

		for (auto e : lt) {
			cout << e << " ";
		}
		cout << endl;

		list<int>lt2(lt);

		for (auto e : lt2) {
			cout << e << " ";
		}
		cout << endl;

		list<int> lt3;
		lt3.push_back(11);
		lt3.push_back(12);
		lt3.push_back(13);

		for (auto e : lt3) {
			cout << e << " ";
		}
		cout << endl;

		lt2 = lt3;

		for (auto e : lt3) {
			cout << e << " ";
		}
		cout << endl;
	}
}