C++中list的使用与模拟实现

#include <iostream>
#include <list>
using namespace std;
int main()
{
    std::list<int> l1; // 构造空的l1
    std::list<int> l2(4, 100); // l2中放4个值为100的元素
    std::list<int> l3(l2.begin(), l2.end()); // 用l2的[begin(), end()）左闭右开的区间构造l3
    std::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 };
    std::list<int> l5(array, array + sizeof(array) / sizeof(int));
    // 用迭代器方式打印l5中的元素
    for (std::list<int>::iterator it = l5.begin(); it != l5.end(); it++)
        std::cout << *it << " ";
    std::cout << endl;
    // C++11范围for的方式遍历
    for (auto& e : l5)
    {
        std::cout << e << " ";
    }
    std::cout << endl;
    return 0;
}

#include <iostream>
#include <list>
using namespace std;
void print_list(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;
}
int main()
{
    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
    for (list<int>::iterator it = l.begin(); it != l.end(); ++it)
    {
        cout << *it << " ";
    }
    cout << endl;
    // 使用反向迭代器逆向打印list中的元素
    for (list<int>::reverse_iterator it = l.rbegin(); it != l.rend(); ++it)
    {
        cout << *it << " ";
    }
    cout << endl;
    return 0;
}

#include <iostream>
#include <list>
using namespace std;
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);
	}
}

#include <iostream>
#include <assert.h>
using std::cout;
using std::endl;
namespace zjx
{
	// List的节点类
	template<class T>
	struct ListNode
	{
		ListNode(const T& val = T())
			:_pPre(nullptr),
			_pNext(nullptr),
			_val(val)
		{
		}
		ListNode<T>* _pPre;
		ListNode<T>* _pNext;
		T _val;
	};
 
	//List的迭代器类
	template<class T, class Ref, class Ptr>
	struct ListIterator
	{
		typedef ListNode<T>* PNode;
		typedef ListIterator<T, Ref, Ptr> Self;
	public:
		ListIterator(PNode pNode = nullptr)
		{
			_pNode = pNode;
		}
		//ListIterator(const Self& l);
 
		Ref operator*()
		{
			return _pNode->_val;
		}
 
		Ptr 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->_pPre;
			return *this;
		}
 
		Self& operator--(int)
		{
			Self tmp(*this);
			_pNode = _pNode->_pPre;
			return tmp;
		}
 
		bool operator!=(const Self& l)
		{
			return _pNode != l._pNode;
		}
 
		bool operator==(const Self& l)
		{
			return _pNode == l._pNode;
		}
 
	public:
		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:
 
		// List的构造
 
		list()
		{
			_pHead = new Node();
			_pHead->_pNext = _pHead;
			_pHead->_pPre = _pHead;
		}
		//构造函数
		list(int n, const T& value = T())
		{
			_pHead = new Node();
			_pHead->_pNext = _pHead;
			_pHead->_pPre = _pHead;
			for (int i = 0; i < n; i++)
			{
				push_back(value);
			}
		}
 
		template <class Iterator>
		list(Iterator first, Iterator last)
		{
			_pHead = new Node();
			_pHead->_pNext = _pHead;
			_pHead->_pPre = _pHead;
			while (first != last)
			{
				push_back(*first);
				first++;
			}
		}
 
		//拷贝构造函数
		list(const list<T>& l)
		{
			//用迭代器先构造出来一个
			list tmp(l.begin(), l.end());
			_pHead = new Node();
			_pHead->_pNext = _pHead;
			_pHead->_pPre = _pHead;
			std::swap(_pHead, tmp._pHead);
		}
 
		list<T>& operator=(list<T> l)
		{
			std::swap(_pHead, l._pHead);
			return *this;
		}
 
		~list()
		{
			clear();
			delete _pHead;
			_pHead = nullptr;
		}
		//List Iterator
		iterator begin()
		{
			return iterator(_pHead->_pNext);
		}
 
		iterator end()
		{
			return iterator(_pHead);
		}
 
		const_iterator begin() const
		{
			return const_iterator(_pHead->_pNext);
		}
 
		const_iterator end() const
		{
			return const_iterator(_pHead);
		}
 
		// List Capacity
		size_t size()const//这个函数右边的const是用来限定this指针的。原本的this指针，不可以改变指向，可以改变所知的内容。
						  //但若要对所指向的内容加以限定的话，那就在函数的右边加上const，表示此函数的隐藏的参数，也就是this指针，被加以const限定。
		{
			size_t count = 0;
			const_iterator cur = begin();
			while (cur != end())
			{
				count++;
				cur++;
			}
			return count;
		}
		//list为空返回1，否则返回0
		bool empty()const
		{
			return size() == 0;
		}
 
		// List Access
 
		T& front()
		{
			return begin()._pNode->_val;
		}
 
		const T& front()const
		{
			return begin()._pNode->_val;
		}
 
		T& back()
		{
			return _pHead->_pPre->_val;
		}
 
		const T& back()const
		{
			return _pHead->_pPre->_val;
		}
 
		// List Modify
 
		//void push_back(const T& val) 
		//{ 
		//    insert(begin(), val); 
		//}
		void push_back(const T& val)
		{
			Node* tail = _pHead->_pPre;
			Node* newnode = new Node(val);
			tail->_pNext = newnode;
			newnode->_pPre = tail;
			newnode->_pNext = _pHead;
			_pHead->_pPre = newnode;
		}
 
		void pop_back()
		{
			erase(--end());
		}
 
		void push_front(const T& val)
		{
			insert(begin(), val);
		}
 
		void pop_front()
		{
			erase(begin());
		}
 
		 在pos位置前插入值为val的节点
 
		iterator insert(iterator pos, const T& val)
		{
			PNode next = pos._pNode;
			PNode prev = next->_pPre;
			PNode newnode = new Node(val);
			newnode->_pNext = next;
			newnode->_pPre = prev;
			prev->_pNext = newnode;
			next->_pPre = newnode;
			return iterator(newnode);
		}
 
		 删除pos位置的节点，返回该节点的下一个位置
 
		iterator erase(iterator pos)
		{
			assert(pos != end());
			PNode next = pos._pNode->_pNext;
			PNode prev = pos._pNode->_pPre;
			delete pos._pNode;
			prev->_pNext = next;
			next->_pPre = prev;
			return iterator(next);
		}
 
		void clear()
		{
			iterator cur = begin();
			while (cur != end())
			{
				erase(cur++);
			}
			_pHead->_pNext = _pHead;
			_pHead->_pPre = _pHead;
		}
 
		//void swap(list<T>& l);
 
	private:
 
		void CreateHead()
		{
			_pHead = new Node();
			_pHead->_pNext = _pHead;
			_pHead->_pPre = _pHead;
		}
		PNode _pHead;
	};
 
};
class Date
{
private:
	int _year;
	int _month;
	int _day;
public:
	Date(int year = 0, int month = 0, int day = 0)
		:_year(year),
		_month(month),
		_day(day)
	{
	}
	void print()
	{
		std::cout << _year << " " << _month << " " << _day << std::endl;
	}
};
int main()
{
	using namespace zjx;
	list<Date> it;
	it.push_back(Date(2022, 5, 16));
	it.push_back(Date(2022, 5, 17));
	it.push_back(Date(2022, 5, 18));
	it.push_back(Date(2022, 5, 19));
	it.push_back(Date(2022, 5, 20));
	for (auto e : it)
	{
		e.print();
	}
	cout << endl;
	list<int> a1(5, 2);
	for (auto e : a1)
	{
		cout << e << " ";
	}
	cout << endl;
	list<Date> a2(it);
	for (auto e : a2)
	{
		e.print();
	}
	cout << endl;
	int arr[] = { 1,2,3,4,5,6,7,8,9 };
	list<int> a3(arr, arr + 9);
	for (auto e : a3)
	{
		cout << e << " ";
	}
	cout << endl;
	a1 = a3;
	for (auto e : a1)
	{
		cout << e << " ";
	}
	cout << endl;
 
	cout << "a3的元素的个数 = " << a3.size() << endl;
 
	list<int> a4;
	cout << a4.empty() << endl;
	const auto ans1 = a3.front();
	auto ans2 = a3.back();
	cout << "ans1 = " << ans1 << " " << "ans2 = " << ans2 << endl;
	a3.push_front(30);
	a3.pop_back();
	a3.pop_front();
	a3.pop_front();
	for (auto e : a3)
	{
		cout << e << " ";
	}
	cout << endl;
	return 0;
}