/* 用链表实现学生成绩信息的管理  */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
struct stud_node{
     int    num;
     char  name[20];
     int    score;
     struct stud_node *next;
};
struct stud_node * Create_Stu_Doc();  /* 新建链表 */
struct stud_node * InsertDoc(struct stud_node * head, struct stud_node *stud); /* 插入 */
struct stud_node * DeleteDoc(struct stud_node * head, int num);  /* 删除 */
void Print_Stu_Doc(struct stud_node * head);  /* 遍历 */
 
int main(void)
{
  struct stud_node *head,*p;
  int choice, num, score;
  char name[20];
  int size = sizeof(struct stud_node);
 
  do{
    printf("1:Create 2:Insert 3:Delete 4:Print 0:Exit\n");
    scanf("%d", &choice);
    switch(choice){
    case 1:  
           head=Create_Stu_Doc();
           break;
    case 2:  
           printf("Input num,name and score:\n");
           scanf("%d%s%d", &num,name, &score);
           p = (struct stud_node *) malloc(size);
           p->num = num;
           strcpy(p->name, name);
           p->score = score;  
           head=InsertDoc(head, p);
           break;
    case 3:  
           printf("Input num:\n");
           scanf("%d", &num);
           head = DeleteDoc(head, num);
           break;
         case 4:  
           Print_Stu_Doc(head);
           break;
         case 0:
          break;
    }
  }while(choice != 0);
 
  return 0;
}
 
/*新建链表*/
struct stud_node * Create_Stu_Doc()   
{  
    struct stud_node * head,*p;
    int num,score;
    char  name[20];
    int size = sizeof(struct stud_node);
 
    head=NULL;
    printf("Input num,name and score:\n");
    scanf("%d%s%d", &num,name, &score);
    while(num != 0){
       p = (struct stud_node *) malloc(size);
       p->num = num;
       strcpy(p->name, name);
       p->score = score;  
       head=InsertDoc(head, p);    /* 调用插入函数 */
       scanf("%d%s%d", &num, name, &score);
   }
   return head;
}
 
/* 插入操作 */
struct stud_node * InsertDoc(struct stud_node * head, struct stud_node *stud)   
{   
   struct stud_node *ptr ,*ptr1, *ptr2;
 
    ptr2 = head;  
    ptr = stud;         /* ptr指向待插入的新的学生记录结点 */
    /* 原链表为空时的插入 */  
    if(head == NULL){  
        head = ptr;         /* 新插入结点成为头结点 */
        head->next = NULL;
    }
    else{             /* 原链表不为空时的插入 */
         while((ptr->num > ptr2->num) && (ptr2->next != NULL)){
            ptr1 = ptr2;     /* ptr1, ptr2各后移一个结点 */
            ptr2 = ptr2->next;
         }
         if(ptr->num <= ptr2->num){     /* 在ptr1与ptr2之间插入新结点 */
            if(head==ptr2)  head = ptr;
            else ptr1->next = ptr;
            ptr->next = ptr2;
        }
        else{                /* 新插入结点成为尾结点 */
            ptr2->next =ptr;
            ptr->next = NULL;  
        }  
    }
    return head;
}
 
/* 删除操作 */
struct stud_node * DeleteDoc(struct stud_node * head, int num)   
{  
    struct stud_node *ptr1, *ptr2;  
 
    /* 要被删除结点为表头结点 */
    if(head!=NULL && head->num == num){   
         ptr2 = head;
         head = head->next;
         free(ptr2);
    }
    if(head == NULL)  /*链表空 */
        return NULL;
     /* 要被删除结点为非表头结点  */
     ptr1 = head;
     ptr2 = head->next; /*从表头的下一个结点搜索所有符合删除要求的结点 */
     while(ptr2!=NULL){
         if(ptr2->num == num){     /* ptr2所指结点符合删除要求 */
             ptr1->next = ptr2->next;
             free(ptr2);  
         }
         else  
             ptr1 = ptr2;       /* ptr1后移一个结点 */
         ptr2 = ptr1->next;     /* ptr2指向ptr1的后一个结点 */
     }
     return head;
}
 
/*遍历操作*/
void Print_Stu_Doc(struct stud_node * head)  
{ struct stud_node * ptr;
   if(head == NULL){
       printf("\nNo Records\n");
       return;
    }
    printf("\nThe Students' Records Are: \n");
    printf("    Num   Name   Score\n");
    for(ptr = head; ptr; ptr = ptr->next)
        printf("%8d%20s%6d \n", ptr->num, ptr->name, ptr->score);
}