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>
  2 #include<malloc.h>
  3 #include<string.h>
  4 struct student
  5 {
  6      int id;
  7      char name[100];
  8      int age;
  9      int sex;
 10      int class_num;
 11      struct student *next;
 12      struct student *pr;
 13 };
 14 typedef struct student link;
 15 link *head;
 16 int insert()
 17 {
 18      link *newnode;
 19      newnode = (link *)malloc(sizeof(struct student));
 20          link *temp_head = head;
 21          printf("请输入学生ID：\n");
 22      scanf("%d",&newnode->id);
 23      printf("请输入学生姓名：\n");
 24      scanf("%s",newnode->name);
 25      printf("请输入学生年龄:\n");
 26      scanf("%d",&newnode->age);
 27      printf("请输入学生性别0(代表男 1代表女):\n");
 28      scanf("%d",&newnode->sex);
 29      if((newnode->sex == 0|| newnode->sex == 1) == 0)
 30      {
 31          printf("input is fail!\n");
 32          scanf("%d",&newnode->sex);
 33      }
 34       printf("请输入学生的班级号码：\n");
 35       scanf("%d",&newnode->class_num);
 36       newnode->next = NULL;
 37       newnode->pr = NULL;
 38          if(temp_head->next == NULL)
 39          {      
 40           temp_head->next = newnode;
 41           newnode->pr = temp_head;
 42           newnode->next = NULL;
 43           return 0;
 44          }
 45    int flag = 0;
 46    while(temp_head->next != NULL)
 47    {    
 48         if(newnode->id < temp_head->next->id)
 49         {
 50              newnode->next = temp_head->next;
 51              newnode->pr = temp_head;
 52              temp_head->next = newnode;
 53              newnode->next->pr = newnode;
 54              flag = 1;
 55              break;
 56          } 
 57         temp_head = temp_head->next;
 58     }
 59     if(flag == 0)
 60       {
 61            temp_head->next = newnode;
 62        newnode->next = NULL;
 63        newnode->pr = temp_head;
 64       }
 65    return 0;
 66 }
 67 int input()
 68 {
 69   char num[100];
 70   scanf("%s",num);
 71   if(strcmp(num,"insert") == 0)
 72   {
 73       return 1;
 74   }
 75   else if(strcmp(num,"delete") == 0)
 76   {
 77       return 2;
 78   }
 79   else if(strcmp(num,"display") == 0)
 80   {
 81       return 3;
 82   }
 83   else if(strcmp(num,"exit") == 0)
 84   {
 85       return 4;
 86   }
 87   else
 88   {
 89       return 0;
 90   }  
 91 }
 92 int display(int id)
 93 {
 94     link *temp_head = head;
 95     int flag = 0;
 96     if(temp_head->next == NULL)
 97     {
 98        printf("没有输入学生信息：\n");
 99        return 0;
100     }
101     while(temp_head != NULL)
102     {
103         if(temp_head->id == id)
104         {
105            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);
106            flag = 1;
107            break;
108      }
109      temp_head = temp_head->next;
110     }
111     if(flag == 0)
112     {
113        printf("查无此人！\n");    
114     }
115     return 0;
116 }
117 int delete(int id)
118 {
119      link *temp_head = head;
120      int flag;
121      if(temp_head->next == NULL)
122      {
123             printf("学生内容为空，无法删除\n");
124             return 0;
125      }
126      while(temp_head != NULL)
127      {
128         if(temp_head->id == id)
129           {
130                 if(temp_head->next == NULL)
131                   {
132                       temp_head->pr->next = NULL;
133                       flag = 1;
134                       break;
135                   }
136               else
137                {
138                  temp_head->pr->next = temp_head->next;
139                  temp_head->next->pr = temp_head->pr;
140                  flag = 1;
141                     break;
142                 }    
143           }
144           temp_head = temp_head->next;
145           
146      }
147      if(flag == 1)
148      {
149          printf("删除成功!\n");
150      }
151      else
152      {
153          printf("删除失败!\n");
154      }
155      return 0;
156 }
157 int main()
158 {
159     int pid;
160     int id;
161     int class_num;
162     head = (link *)malloc(sizeof(struct student));
163     head->next = NULL;
164     head->pr = NULL;
165     printf("/****************************\n");
166     printf("\t欢迎使用学生管理系统\n");
167     printf("\t输入insert添加学生信息\n");
168     printf("\t输入delete删除学生信息\n");
169     printf("\t输入display查看学生信息\n");
170     printf("\t输入exit退出程序\n");
171     printf("*************************/\n");
172     printf("请输入命令！\n");
173     pid = input();
174     while(pid != 4)
175     {
176         switch(pid)
177         {
178           case 1 :
179                     insert();
180                 break;
181           case 2 :
182                 printf("请输入要删除的学生ID：\n");
183             scanf("%d",&id);
184             delete(id);
185                     break;
186           case 3 :
187                 printf("请输入要显示的学生ID：\n");
188             scanf("%d",&id);
189             display(id);
190                     break;
191           case 0 :
192                     printf("输入的命令有误，请重新输入：\n");
193                 break;
194           case 4 :
195                     break;
196          }
197      printf("请输入命令！\n");
198      pid = input();
199    }
200    printf("该程序结束！\n");
201     return 0;
202 }