程序代码：

#include<stdio.h>
#include<stdlib.h>
struct student 
{
    int num;
    char name[30];
    int score;
    struct student * pnext;
};
struct student * creat_list(struct student * h);  //建立单链表 
void print_list(struct student * h);              //输出单链表 
void search_list(struct student * h);             //搜寻函数 
int main()
{
    struct student * head;
    char ren;
    head = NULL;
    printf("请输入学生信息，直至序号为0为止\n");
    head = creat_list(head);
    printf("----------------------------------------\n");
    print_list(head); 
    printf("----------------------------------------\n");
    search_list(head);
}
struct student * creat_list(struct student * h)    //建立单链表 ，这一段没有问题 
{
    struct student * p1,*p2;
    p1 = p2 = (struct student *)malloc(sizeof(struct student));
    printf("请输入学生学号：");
    scanf("%d",&p2 -> num);
    printf("请输入学生姓名：");
    scanf("%s",&p2 -> name);
    printf("请输入学生成绩：");
    scanf("%d",&p2 -> score);
    p2 -> pnext = NULL;
    while(p2 -> num != 0)
    {
        if(h == NULL)
           h = p2;
        else
           p1 -> pnext = p2;
        p1 = p2;
        p2 = (struct student *)malloc(sizeof(struct student));
        if(p2 != NULL)
        {
            printf("请输入学生学号：");
            scanf("%d",&p2 -> num);
            if(p2 -> num == 0) break;
             printf("请输入学生姓名：");
            scanf("%s",&p2 -> name);
            printf("请输入学生成绩：");
            scanf("%d",&p2 -> score);
            p2 -> pnext = NULL;
        }
    } 
    return h;
}
void print_list(struct student * h)      //输出单链表函数，没有问题 
{
    struct student * temp;
    temp = h;
    printf("学号\t姓名\t成绩\n");
    while(temp != NULL)
    {
        printf("%d\t%s\t%d",temp -> num,temp -> name,temp -> score);
        printf("\n");
        temp = temp -> pnext;
    }
}
void search_list(struct student * h)    //搜寻函数，用来寻找学生学号！ 
{
    struct student * temp;
    int date;
    char x;
    temp = h;
    printf("是否进行查询工作？(y/n): ");
    scanf("%d",&x); 
    if(x == 'y')
    { 
        printf("请输入学生学号：\n");    //就是这一段！为什么程序就没有执行呢？ 
        scanf("%d",&date);               // 直接就结束了呢？
        if(date == 0) 
            printf("查无此人，请重输！");
        while(temp != NULL)
        {
            if(date == temp -> num)
            {
               printf("学号\t姓名\t成绩\n");
               printf("%d\t%s\t%d",temp -> num,temp -> name,temp -> score);
            }
            else
               temp = temp -> pnext;
        }
    } 
}