2. 写程序对单链表进行排序.

下面是对单链表进行排序的示例程序，使用冒泡排序算法：

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

// 定义链表节点结构体
typedef struct Node {
    int data;
    struct Node *next;
} Node;

// 创建链表
Node *createList(int arr[], int n) {
    Node *head = NULL, *tail = NULL;
    for (int i = 0; i < n; i++) {
        Node *p = (Node *) malloc(sizeof(Node));
        p->data = arr[i];
        p->next = NULL;
        if (head == NULL) {
            head = tail = p;
        } else {
            tail->next = p;
            tail = p;
        }
    }
    return head;
}

// 打印链表
void printList(Node *head) {
    for (Node *p = head; p != NULL; p = p->next) {
        printf("%d ", p->data);
    }
    printf("\n");
}

// 对链表进行排序
void sortList(Node *head) {
    for (Node *p = head; p != NULL; p = p->next) {
        for (Node *q = p->next; q != NULL; q = q->next) {
            if (p->data > q->data) {
                int temp = p->data;
                p->data = q->data;
                q->data = temp;
            }
        }
    }
}

int main() {
    int arr[] = {5, 3, 1, 4, 2};
    int n = sizeof(arr) / sizeof(arr[0]);
    Node *head = createList(arr, n);
    printf("原始链表：");
    printList(head);
    sortList(head);
    printf("排序后链表：");
    printList(head);
    return 0;
}

程序运行结果如下：

原始链表：5 3 1 4 2
排序后链表：1 2 3 4 5