void del_account(FILE *fp,int accountnum)//删除账号信息模块
{
    int i;
    if(search_account(fp,accountnum)==0)
    printf("无法找到此账户！\n");
    else
    {
        for(i = 0;i<cur_account-1;i++)
            if(accountcollection[i].account != accountnum)
              fprintf(fp,"%d %d %s %.2f\n",
                      accountcollection[i].account,accountcollection[i].key,accountcollection[i].name,accountcollection[i].balance);
    printf("删除成功!\n");
    }
}