#include <stdio.h>#include <stdlib.h>//定义节点typedef struct Node{    int data;    struct Node * PNext;}*PNode,Node;//初始化函数PNode create_list();//创建节点//打印出链表void traverse_list(PNode);//删除节点pos  从1 开始void delete_node(PNode,int,int *);//插入节点  pos 从1开始void insert_data(PNode,int ,int );void main(){    //int val;    //定义头指针    PNode PHead=NULL;    PHead=create_list();            //delete_node(PHead,-1,&val);        insert_data(PHead,-2,2);    traverse_list(PHead);}PNode create_list(){    int len;    int i;    int val;    //定义头节点    PNode PHead=(PNode)malloc(sizeof(Node));    //内存不足等情况会出现分配内存失败的情况  发生错误会返回NULL    if(PHead == NULL){        printf("内存分配失败");    }    PNode Ptail=PHead;    //将头节点的指针域指向NULL  如果没有首节点指针域就是NULL     Ptail->PNext=NULL;    /*        思路：            定义节点ptail，永远指向尾节点，一开始只有头结点 头结点也是尾节点，所以指向头结点                    将新建的PNew节点挂载到ptail节点后面，挂载好之后，ptail指向新建的PNew节点，这样保证ptail永远指向尾节点    */    printf("请输入初始化节点的数量\n");    scanf("%d",&len);    for(i=0;i<len;i++){        printf("请输入节点的值");        scanf("%d",&val);        PNode PNew=(PNode)malloc(sizeof(Node));        PNew->data=http://www.mamicode.com/val;        Ptail->PNext=PNew;        PNew->PNext=NULL;        Ptail=PNew;    }    //返回首节点    return PHead;}void traverse_list(PNode PHead){    PNode p = PHead->PNext;    //printf("%d\n",PHead->PNext);    if(p == NULL)    {        printf("链表为空\n");        exit(0);    }    while(p != NULL){        printf("%d\n",p->data);        p=p->PNext;    }}void delete_node(PNode PHead,int pos,int * val){        int i=0;    if(PHead->PNext==NULL){        printf("节点为空");        exit(0);    }    if(pos <0){        printf("没有数据");        exit(0);    }    PNode p=PHead;    PNode t;    PNode r;    while(i != pos){        //printf("%d\n",i=t->data);exit(0);        t=p;        if(i == pos-1){            //printf("%d\n",i=p->PNext->PNext->data);exit(0);            //exit(0);            r=p->PNext;            t->PNext=p->PNext->PNext;            free(r);            r=NULL;            //exit(0);            return;        }        i++;        p=p->PNext;    }}void insert_data(PNode PHead,int pos,int val){    int i=0;    PNode p=PHead;    while(p != NULL && i<pos-1){        p=p->PNext;        i++;    }    if(p == NULL || i>pos -1){        printf("插入错误");        return ;    }    PNode PNew=(PNode)malloc(sizeof(Node));    if(PNew == NULL){        printf("内存分配失败");        exit(-1);    }    PNode t=p->PNext;    PNew->data=http://www.mamicode.com/val;    PNew->PNext=t;    p->PNext=PNew;}