学生信息管理系统（C语言版本）

这是我个人写的一个学生管理系统，这是我仅仅用来练手的代码，要知道链表可是你在面试过程中最大机率会考到的，我是陆续从单向链表入门，然后采用双向链表写的代码！如有BUG，请指正，让我们
共同进步！ 
 1 #include<stdio.h>
 #include<malloc.h>
 #include<string.h>
 struct student
 {
      int id;
      char name[];
      int age;
      int sex;
      int class_num;
      struct student *next;
      struct student *pr;
 };
 typedef struct student link;
 link *head;
 int insert()
 {
      link *newnode;
      newnode = (link *)malloc(sizeof(struct student));
          link *temp_head = head;
          printf("请输入学生ID：\n");
      scanf("%d",&newnode->id);
      printf("请输入学生姓名：\n");
      scanf("%s",newnode->name);
      printf("请输入学生年龄:\n");
      scanf("%d",&newnode->age);
      printf("请输入学生性别0(代表男 1代表女):\n");
      scanf("%d",&newnode->sex);
      if((newnode->sex == || newnode->sex == ) == )
      {
          printf("input is fail!\n");
          scanf("%d",&newnode->sex);
      }
       printf("请输入学生的班级号码：\n");
       scanf("%d",&newnode->class_num);
       newnode->next = NULL;
       newnode->pr = NULL;
          if(temp_head->next == NULL)
          {
           temp_head->next = newnode;
           newnode->pr = temp_head;
           newnode->next = NULL;
           return ;
          }
    int flag = ;
    while(temp_head->next != NULL)
    {
         if(newnode->id < temp_head->next->id)
         {
              newnode->next = temp_head->next;
              newnode->pr = temp_head;
              temp_head->next = newnode;
              newnode->next->pr = newnode;
              flag = ;
              break;
          }
         temp_head = temp_head->next;
     }
     if(flag == )
       {
            temp_head->next = newnode;
        newnode->next = NULL;
        newnode->pr = temp_head;
       }
    return ;
 }
 int input()
 {
   char num[];
   scanf("%s",num);
   if(strcmp(num,"insert") == )
   {
       return ;
   }
   else if(strcmp(num,"delete") == )
   {
       return ;
   }
   else if(strcmp(num,"display") == )
   {
       return ;
   }
   else if(strcmp(num,"exit") == )
   {
       return ;
   }
   else
   {
       return ;
   }
 }
 int display(int id)
 {
     link *temp_head = head;
     int flag = ;
     if(temp_head->next == NULL)
     {
        printf("没有输入学生信息：\n");
        return ;
     }
     while(temp_head != NULL)
     {
         if(temp_head->id == id)
         {
            printf("id = %d\n name = %s\n age = %d\n sex = %d\n class_num = %d\n",temp_head->id,temp_head->name,temp_head->age,temp_head->sex,temp_head->class_num);
            flag = ;
            break;
      }
      temp_head = temp_head->next;
     }
     if(flag == )
     {
        printf("查无此人！\n");
     }
     return ;
 }
 int delete(int id)
 {
      link *temp_head = head;
      int flag;
      if(temp_head->next == NULL)
      {
             printf("学生内容为空，无法删除\n");
             return ;
      }
      while(temp_head != NULL)
      {
         if(temp_head->id == id)
           {
                 if(temp_head->next == NULL)
                   {
                       temp_head->pr->next = NULL;
                       flag = ;
                       break;
                   }
               else
                {
                  temp_head->pr->next = temp_head->next;
                  temp_head->next->pr = temp_head->pr;
                  flag = ;
                     break;
                 }
           }
           temp_head = temp_head->next;

      }
      if(flag == )
      {
          printf("删除成功!\n");
      }
      else
      {
          printf("删除失败!\n");
      }
      return ;
 }
 int main()
 {
     int pid;
     int id;
     int class_num;
     head = (link *)malloc(sizeof(struct student));
     head->next = NULL;
     head->pr = NULL;
     printf("/****************************\n");
     printf("\t欢迎使用学生管理系统\n");
     printf("\t输入insert添加学生信息\n");
     printf("\t输入delete删除学生信息\n");
     printf("\t输入display查看学生信息\n");
     printf("\t输入exit退出程序\n");
     printf("*************************/\n");
     printf("请输入命令！\n");
     pid = input();
     while(pid != )
     {
         switch(pid)
         {
           case  :
                     insert();
                 break;
           case  :
                 printf("请输入要删除的学生ID：\n");
             scanf("%d",&id);
             delete(id);
                     break;
           case  :
                 printf("请输入要显示的学生ID：\n");
             scanf("%d",&id);
             display(id);
                     break;
           case  :
                     printf("输入的命令有误，请重新输入：\n");
                 break;
           case  :
                     break;
          }
      printf("请输入命令！\n");
      pid = input();
    }
    printf("该程序结束！\n");
     return ;
 }