编写一个c语言程序，以单链表的首结点值x为基准将该单链表分割为两个部分，使所有小于x的结点排在大于或等于x的结点之前

编写C语言程序来分割单链表可以根据给定的节点值`x`将链表分为两部分。这里是一个简单的示例，我们将创建一个函数`splitList`，它接受链表的头节点`head`以及基准值`x`作为输入：

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

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

// 插入新节点到链表
ListNode* insertNode(ListNode *head, int val) {
    ListNode *new_node = (ListNode*)malloc(sizeof(ListNode));
    new_node->val = val;
    new_node->next = head;
    return new_node;
}

// 比较并分割链表
void splitList(ListNode **head, int x) {
    ListNode *smaller_head = NULL, *smaller_tail = NULL;
    ListNode *greater_head = head, *current = *head;

    while (current != NULL) {
        if (current->val < x) {
            if (!smaller_head) {
                smaller_head = current;
                smaller_tail = current;
            } else {
                smaller_tail->next = current;
                smaller_tail = current;
            }
        } else {
            if (!greater_head) {
                greater_head = current;
            } else {
                (*greater_head)->next = current;
            }
        }

        current = current->next;
    }

    // 将小链表连接到大链表前
    if (smaller_head) {
        smaller_tail->next = greater_head;
        *head = smaller_head;
    } else {
        *head = greater_head;
    }
}

// 打印链表
void printList(ListNode *head) {
    ListNode *temp = head;
    while (temp != NULL) {
        printf("%d ", temp->val);
        temp = temp->next;
    }
    printf("\n");
}

int main() {
    // 创建一个测试链表
    ListNode *head = insertNode(NULL, 5);
    insertNode(head, 2);
    insertNode(head, 8);
    insertNode(head, 1);
    insertNode(head, 9);

    int x = 5;
    printf("Original List: ");
    printList(head);

    splitList(&head, x);

    printf("Split List with %d as pivot: \n", x);
    printList(head);

    return 0;
}

在这个例子中，我们首先创建了一个单链表，然后调用`splitList`函数根据`x=5`分割链表。之后打印原始链表和分割后的链表。