4)程序功能：输入若干个学生成绩（输入-1为结束标志），建立两个已按升序排序的单向链表，头指针分别为list1、list2，把两个链表拼成一个升序排序的新链表，并输出新链表信息。要求自定义函数，实现将两个链表拼成一个链表，并返回拼组后的新链表。

可以使用以下代码实现：

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

typedef struct Node {
int data;
struct Node *next;
} Node;

Node *mergeLists(Node *list1, Node *list2) {
Node *head = NULL;
Node **tail = &head;

while (list1 && list2) {
if (list1->data < list2->data) {
*tail = list1;
list1 = list1->next;
} else {
*tail = list2;
list2 = list2->next;
}
tail = &((*tail)->next);
}

*tail = (list1 ? list1 : list2);

return head;
}

int main() {
Node *list1 = NULL;
Node *list2 = NULL;
int score;

printf("请输入学生成绩（输入-1为结束标志）：\n");

while (1) {
scanf("%d", &score);
if (score == -1) {
break;
}

Node *node = (Node *)malloc(sizeof(Node));
node->data = score;
node->next = NULL;

if (!list1 || score < list1->data) {
node->next = list1;
list1 = node;
} else {
Node *prev = list1;
Node *cur = list1->next;

while (cur && score >= cur->data) {
prev = cur;
cur = cur->next;
}

node->next = cur;
prev->next = node;
}
}

printf("第一个链表为：\n");
Node *cur = list1;
while (cur) {
printf("%d ", cur->data);
cur = cur->next;
}
printf("\n");

printf("请输入学生成绩（输入-1为结束标志）：\n");

while (1) {
scanf("%d", &score);
if (score == -1) {
break;
}

Node *node = (Node *)malloc(sizeof(Node));
node->data = score;
node->next = NULL;

if (!list2 || score < list2->data) {
node->next = list2;
list2 = node;
} else {
Node *prev = list2;
Node *cur = list2->next;

while (cur && score >= cur->data) {
prev = cur;
cur = cur->next;
}

node->next = cur;
prev->next = node;
}
}

printf("第二个链表为：\n");
cur = list2;
while (cur) {
printf("%d ", cur->data);
cur = cur->next;
}
printf("\n");

Node *mergedList = mergeLists(list1, list2);

printf("合并后的链表为：\n");
cur = mergedList;
while (cur) {
printf("%d ", cur->data);
cur = cur->next;
}
printf("\n");

return 0;
}