实验11-2-2 学生成绩链表处理（20 分）

本题要求实现两个函数，一个将输入的学生成绩组织成单向链表；另一个将成绩低于某分数线的学生结点从链表中删除。

函数接口定义：

1 2	struct stud_node createlist(); struct stud_node deletelist( struct stud_node *head, int min_score );

函数createlist利用scanf从输入中获取学生的信息，将其组织成单向链表，并返回链表头指针。链表节点结构定义如下：

struct stud_node {
    int              num;      /*学号*/
    char             name[20]; /*姓名*/
    int              score;    /*成绩*/
    struct stud_node *next;    /*指向下个结点的指针*/
};

输入为若干个学生的信息（学号、姓名、成绩），当输入学号为0时结束。

函数deletelist从以head为头指针的链表中删除成绩低于min_score的学生，并返回结果链表的头指针。

裁判测试程序样例：

#include <stdio.h>
#include <stdlib.h>

struct stud_node {
     int    num;
     char   name[20];
     int    score;
     struct stud_node *next;
};

struct stud_node *createlist();
struct stud_node *deletelist( struct stud_node *head, int min_score );

int main()
{
    int min_score;
    struct stud_node *p, *head = NULL;

    head = createlist();
    scanf("%d", &min_score);
    head = deletelist(head, min_score);
    for ( p = head; p != NULL; p = p->next )
        printf("%d %s %d\n", p->num, p->name, p->score);

    return 0;
}

/* 你的代码将被嵌在这里 */

输入样例：

1 zhang 78
2 wang 80
3 li 75
4 zhao 85
0
80

输出样例：

1 2	2 wang 80 4 zhao 85

#include <stdio.h>
#include <stdlib.h>

struct stud_node {
     int    num;
     char   name[20];
     int    score;
     struct stud_node *next;
};

struct stud_node *createlist();
struct stud_node *deletelist( struct stud_node *head, int min_score );

int main()
{
    int min_score;
    struct stud_node *p, *head = NULL;

    head = createlist();
    scanf("%d", &min_score);
    head = deletelist(head, min_score);
    for ( p = head; p != NULL; p = p->next )
        printf("%d %s %d\n", p->num, p->name, p->score);

    return 0;
}

struct stud_node *createlist()
{
    struct stud_node *head, *tail, *q;
    head = tail = NULL;
    int num;
    scanf ("%d", &num);
    while (num != 0)
    {
        q = (struct stud_node *)malloc (sizeof (struct stud_node));
        scanf ("%s %d", q->name, &q->score);
        q->num = num;
        q->next = NULL;
        if (head == NULL)
            head = q;
        else
            tail->next = q;
        tail = q;
        scanf ("%d", &num);
    }
    return head;
}
struct stud_node *deletelist( struct stud_node *head, int min_score )
{
    struct stud_node *ptr1, *ptr2;
    while (head != NULL && head->score < min_score)
    {
        ptr2 = head;
        head = head->next;
        free(ptr2);
    }
    if (head == NULL)
        return NULL;
    ptr1 = head;
    ptr2 = head->next;
    while (ptr2 != NULL)
    {
        if (ptr2->score < min_score) {
            ptr1->next = ptr2->next;
            free(ptr2);
        }
        else
            ptr1 = ptr2;
        ptr2 = ptr1->next;
    }
    return head;
}