C双链表（增、删、改、查）

#define _CRT_SECURE_NO_WARNINGS
#include "stdio.h"
#include "windows.h"

//链表结构体
typedef struct node
{
	int id;
	struct node *pre;
	struct node *next;
}NODE;

//初始化头节点
NODE *init()
{
	NODE *p = (NODE *)malloc(sizeof(NODE));
	p->pre = NULL;
	p->next = NULL;
	return p;
}

//插入节点
void insert(NODE *head, NODE data, int x)
{
	NODE *p = (NODE *)malloc(sizeof(NODE));
	*p = data;
	if (1 == x)
	{
		p->next = head->next;
		head->next = p;
		p->pre = head;
		if (p->next != NULL)
		{
			p->next->pre = p;
		}
	}
	else if (2 == x)
	{
		NODE *q = head;
		while (q->next != NULL)
		{
			q=q->next;
		}
		p->next = q->next;
		q->next = p;
		p->pre = q;
	}
}

//修改节点数据
void alert(NODE *head, int id, NODE data)
{
	NODE *p = head->next;
	while (p != NULL)
	{
		if ((p->id) == id)
		{
			data.next = p->next;
			data.pre = p->pre;
			*p = data;
		}
		p = p->next;
	}
}

//删除节点及数据
void delet(NODE *head, int ad)
{
	NODE *p = head->next;
	NODE *q = head;
	while (p != NULL)
	{
		NODE *a = NULL;
		if (p->id == ad)
		{
			a = p;
			p = p->next;
			if (p != NULL)
			{
				p->pre = q;
			}
			q->next = p;
			free(a);
		}
		else
		{
			p = p->next;
			q = q->next;
		}
	}
}

//输出节点数据
void print(NODE *head)
{
	NODE *p = head->next;
	while (p != NULL)
	{
		printf("%d ", p->id);
		p = p->next;
	}
	printf("\n\n");
}


int main()
{
	NODE *head = init();
	NODE ini;
	while (1)
	{
		printf("请输入操作功能：\n--1--输入数据\n--2--删除数据\n--3--修改数据\n--4--显示数据\n--5--退出\n");
		printf("选择：");
		int n;
		scanf("%d", &n);
		switch (n)
		{
		case 1:
			printf("请输入插入方式--1--头插 --2--尾插\n");
			printf("选择：");
			int x;
			scanf("%d", &x);
			printf("请输入插入数据，以'0'结束\n");
			while (1)
			{
				scanf("%d", &ini.id);
				if (ini.id == 0)break;
				insert(head, ini, x);
			}
			system("cls");
			break;
		case 2:
			system("cls");
			print(head);
			printf("请输入要删除的数据：");
			int did;
			scanf("%d", &did);
			delet(head, did);
			system("cls");
			break;
		case 3:
			system("cls");
			print(head);
			printf("请输入要修改的数据：");
			int aid;
			scanf("%d", &aid);
			printf("将被修改的数据改为：");
			scanf("%d", &ini.id);
			alert(head, aid, ini);
			system("cls");
			break;
		case 4:
			system("cls");
			print(head);
			break;
		case 5:
			return 0;
			break;
		default:
			system("cls");
			printf("输入错误，请重新输入：");
			break;
		}
	}
	system("pause");
	return 0;
}