C++单向链表实现

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#include <iostream>
typedef int Rank;
struct Node
{
	int data;
	Node* pnode;
};

class mylist
{
private:
	int size;
	Node header;
public:
	mylist() { size = 0; header.data = NULL; header.pnode = NULL; }
	bool insertasfirst(int elem); //作为首节点插入
	bool removefirst(); //删除首节点
	bool insertaslast(int elem); //作为尾节点插入
	bool removelast(); //删除尾节点
	bool insert(Rank r, int elem); //在秩为r的位置插入
	void clear();
	void show();
	~mylist() { clear(); };
};

bool mylist::insertasfirst(int elem)
{
	if (size == 0)
	{
		header.pnode = new Node;
		header.pnode->data = elem;
		header.pnode->pnode = NULL;
		size++;
		return true;
	}
	else if (size >0)
	{
		Node* oldnode = header.pnode;
		header.pnode = new Node;
		header.pnode->data = elem;
		header.pnode->pnode = oldnode;
		size++;
		return true;
	}
	else return false;
}

bool mylist::removefirst()
{
	if (header.pnode != NULL)
	{
		Node* temp = header.pnode;
		if (header.pnode->pnode)
			header.pnode = header.pnode->pnode;
		else
			header.pnode = NULL;
		delete temp;
		size -- ;
		return true;
	}
	else return false;
}

void mylist::show()
{
	if (size == 0)
	{
		std::cout << "there is no Node";
		return;
	}
	Node* p = header.pnode;
	for (int i = 0; i < size; i++)
	{
		std::cout << p->data << " ";
		if(p->pnode)
			p = p->pnode;
	}
}

void mylist::clear()
{
	if (size == 0) return;
	while (header.pnode->pnode != NULL)
	{
		Node* temp = header.pnode;
		header.pnode = header.pnode->pnode;
		delete temp;
		size--;
	}
	delete header.pnode;
	header.pnode = NULL;
	size--;
}

bool mylist::insertaslast(int elem)
{
	if (size == 0)
	{
		header.pnode = new Node;
		header.pnode->data = elem;
		header.pnode->pnode = NULL;
		size++;
		return true;
	}
	Node*temp = &header;
	while (temp->pnode != NULL)
	{
		temp = temp->pnode;
	}
	temp->pnode = new Node;
	temp->pnode->data = elem;
	temp->pnode->pnode = NULL;
	size++;
	return true;
}

bool mylist::removelast()
{
	if (size == 0) return false;
	Node* temp = header.pnode;
	Node* header_pnode=header.pnode;
	while (header.pnode->pnode != NULL)
	{
		temp = header.pnode;
		header.pnode = header.pnode->pnode;
	}
	temp->pnode = NULL;
	delete header.pnode;
	header.pnode = header_pnode;
	size--;
	return true;
}

bool mylist::insert(Rank r, int elem)
{
	if (r < 0 || r >size) return false;
	Node* pred = header.pnode;
	Node* header_pnode = header.pnode;
	for (int i = 0; i < r; i++)
	{
		pred = header.pnode;
		header.pnode = header.pnode->pnode;
	}
	pred->pnode = new Node;
	pred->pnode->data = elem;
	pred->pnode->pnode = header.pnode;
	header.pnode = header_pnode;
	size++;
	return true;
}