双向链表的存储读出数据修改的程序//为何崩溃

C/C++ code

#include <iostream>#include <string>#include <cstring>#include <fstream>using namespace std;struct table{    table():next(NULL),prev(NULL){};    table(int id_t,char* name_t,int age_t):        id(id_t),name(name_t),age(age_t),next(NULL),prev(NULL){}    int id;    char* name;    int age;    table* next;    table* prev;};table* ifRead(char* file)//读出文件函数实现{    table* head=NULL,*memory=NULL,*cur=NULL,*tail=NULL;    ifstream iff(file);    iff.seekg(0,ios::beg);    char str[8]="";    int count=0;    while(iff.getline(str,sizeof(str),' '))//读出操作与存入链表中        if(++count==1)        {            memory = new table;            if(head==NULL&&tail==NULL)            {                head=memory;                tail=memory;                int temp=0;                int i=0;                while(str[i]!='\0')                {                    str[i]-=48;                    temp=temp*10+str[i];                    i++;                }                memory->id=temp;            }            else            {                tail->next=memory;                memory->prev=tail;                tail=memory;                int temp=0;                int i=0;                while(str[i]!='\0')                {                    str[i]-=48;                    temp=temp*10+str[i];                    i++;                }                memory->id=temp;            }        }        else if(count==2)        {            memory->name=str;        }        else if(count==3)        {            int temp=0;            int i=0;            while(str[i]!='\0')            {                str[i]-=48;                temp=temp*10+str[i];                i++;            }            memory->age=temp;            count=0;        }    iff.close();    return head;}void revise(table* head,char* fname)//修改完毕并存入文件中{    cout<<"input student's id that you want to midfy"<<endl;    int id_modfiy;    cin>>id_modfiy;    table* cur=head;    while(cur!=NULL)    {        if(cur->id==id_modfiy)        {            cout<<"1.Do you want to modify the student's id"                <<"2.Do you want to modify the student's name"                <<"3.Do you want to modify the student's age"                <<"4.Do you want to modify the student's whole information"                <<endl;            int choice;            cin>>choice;            switch(choice)            {                case 1:cin>>cur->id;break;                case 2:cin>>cur->name;break;                case 3:cin>>cur->age;break;                case 4:cin>>cur->name>>cur->id>>cur->age;break;            }        }        cur=cur->next;    }}int main(){        char fname[10]="";    cout<<"input student's information table file name"<<endl;    cin>>fname;    table* head=ifRead(fname);    revise(head,fname);}

C/C++ code

    if(++count==1)        {            memory = new table;            if(head==NULL&&tail==NULL)            {/*为什么不初始化memory节点内部的next和prev指针？？？name指针为什么不申请内存存放数据，而是指向了一个你用来存放临时数据的buff呢？？还是就是与这个if匹配的else有何作用呢？我发现好像根本就不可能进入到这个else里面。*/                head=memory;                tail=memory;                int temp=0;                int i=0;                while(str[i]!='\0')                {                    str[i]-=48;                    temp=temp*10+str[i];                    i++;                }                memory->id=temp;            }            else            {                tail->next=memory;                memory->prev=tail;                tail=memory;                int temp=0;                int i=0;                while(str[i]!='\0')                {                    str[i]-=48;                    temp=temp*10+str[i];                    i++;                }                memory->id=temp;            }        }