单链表的简单实现

关于单链表的操作中，关系到头节点创建和更改的要用二级指针或者一级指针引用，其他的可用一级指针

#pragma once
#include<iostream>
#include<assert.h>
using namespace std;

typedef struct ListNode
{
	int data;
	struct ListNode* next;
}Node;

void PrintList(Node* head);
Node* BuyNode(int x);//创造新节点
void PushBack(Node* &head,int x);
void PushFront(Node* &head,int x);
void PopBack(Node* &head);
void PopFront(Node* &head);
Node* Find(Node* head,int x);
void Destory(Node* &head);//清空链表
void Insert(Node* &head, Node* pos, int x);
void Erase(Node* &head, Node* pos);

//输出链表
void PrintList(Node* head)
{
	if (NULL == head)
	{
		cout << "空链表"<<endl;
		return;
	}
	Node* cur = head;
	while (cur)
	{
		cout << cur->data << "->";
		cur = cur->next;
	}
	cout << "NULL" << endl;
}
//创造新节点
Node* BuyNode(int x)
{
	Node* cur = (Node*)malloc(sizeof(Node));
	cur->data = x;
	cur->next = NULL;
	return cur;
}
//尾插
void PushBack(Node* &head, int x)
{//空 或者 不空
	if (NULL == head)
	{
		head = BuyNode(x);
	}
	else
	{
		Node* cur = head;
		while (cur->next)
		{
			cur = cur->next;
		}
		cur->next = BuyNode(x);
	}
}
//头插
void PushFront(Node* &head, int x)
{//空 或者 不空
	if (NULL == head)
		head = BuyNode(x);
	else
	{
		Node* cur = BuyNode(x);
		cur->next = head;
		head = cur;
	}
}
//尾删
void PopBack(Node* &head)
{
	if (NULL == head)            //空
		return;
	else if (NULL == head->next)//一个
	{
		free(head);
		head = NULL;
	}
	else
	{
		Node* cur = head;        //多个
		while (cur->next->next)
		{
			cur = cur->next;
		}free(cur->next);
		cur->next = NULL;
	}
}
//头删
void PopFront(Node* &head)
{
	if (NULL == head)          //空的
		return;
	else if (head->next==NULL) //一个
	{
		free(head);
		head = NULL;
	}
	else
	{
		Node* cur = head->next;//多个
		free(head);
		head = cur;
	}
}

Node* Find(Node* head,int x)
{
	while (head)
	{
		if (head->data == x)
			return head;
		else
			head = head->next;
	}
	return NULL;
}
//清空链表
void Destory(Node* &head)
{
	if (head == NULL)
		return;
	Node* cur = head;
	while (cur)
	{
		Node* next = cur->next;
		free(cur);
		cur = next;
	}
	head = NULL;
}
//在pos前面插入元素x
void Insert(Node* &head, Node* pos, int x)
{
	assert(head);
	assert(pos);
	if (head == pos)
		PushFront(head,x);
	else
	{
		Node* cur=head;
		while (cur->next!=pos)
		{
			cur = cur->next;
		}
		Node* newNode = BuyNode(x);
		newNode->next = cur->next;
		cur->next = newNode;

	}
}
//指定位置删除
void Erase(Node* &head, Node* pos)
{
	assert(head);
	assert(pos);
	if (pos == head)
		PopFront(head);
	else
	{
		Node* cur = head;
		while (cur->next != pos)
		{
			cur = cur->next;
		}
		cur->next = pos->next;
		free(pos);
		pos = NULL;
	}
}

int main()
{
	Node* list = NULL;
	PushBack(list, 2);
	PushBack(list, 3);
	PushBack(list, 5);
	PushBack(list, 6);
	PushFront(list, 1);
	PushFront(list, 0);
	PrintList(list);
	PopBack(list);
	PopFront(list);
	PrintList(list);
	Node* pos1=Find(list,5);
	Insert(list, pos1, 4); PrintList(list);
	Node* pos2 = Find(list, 3);
	Erase(list,pos2);
	PrintList(list);
	Destory(list);
	PrintList(list);
	system("pause");
	return 0;
}