【唉呀哎呀】今天考试这个题

#include <stdio.h>

#include <stdlib.h>



typedef struct _ListHead

{

    struct _ListHead* pre;

    struct _ListHead* next;

} ListHead;



typedef struct _Data

{

    ListHead list_head;

    int id;

} Data;



int main()

{

    int i =0;

    const int maxData = 32;

    Data* head = NULL;

    Data* tail = NULL;

    Data* newData= NULL;

    Data* pData= NULL;





    for(i = 0; i < maxData; i++)

    {

        newData = (Data*)malloc(sizeof(Data));

        if(!newData)

        {

            printf("no mem");

            return -1;

        }

        memset(newData, 0, sizeof(Data));



        newData->id = i;

        if(!head)

        {

            head = newData;

            tail = head;

        }

        else

        {

            tail->list_head.next = newData;

            newData->list_head.pre = tail;

            tail = newData;

        }

    }



    pData = head;

    if(!pData)

    {

        printf("null \n");

    }

    while(pData)

    {

        printf("id:%d\n",pData->id);

        pData = pData->list_head.next;

    }

    return 0;

}

 在办公室一个小时都没写完，回来15分钟测完啥情况啊啊啊啊。