2．编写一个c语言程序，使用单链表，以给定值x为基准将单链表分割成两部分，所有小于x的结点排在大于或等于x的结点之前，不需要排序。

好的，关于你的问题，以下是示例代码：

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

typedef struct ListNode {
    int val;
    struct ListNode *next;
} ListNode;

ListNode* partition(ListNode* head, int x) {
    ListNode *dummy1 = (ListNode *)malloc(sizeof(ListNode));
    ListNode *dummy2 = (ListNode *)malloc(sizeof(ListNode));
    ListNode *cur1 = dummy1, *cur2 = dummy2;

    while (head != NULL) {
        if (head->val < x) {
            cur1->next = head;
            cur1 = cur1->next;
        } else {
            cur2->next = head;
            cur2 = cur2->next;
        }
        head = head->next;
    }

    cur1->next = dummy2->next;
    cur2->next = NULL;
    ListNode *res = dummy1->next;

    free(dummy1);
    free(dummy2);
    return res;
}

int main() {
    ListNode *head = (ListNode *)malloc(sizeof(ListNode));
    head->val = 1;
    head->next = (ListNode *)malloc(sizeof(ListNode));
    head->next->val = 4;
    head->next->next = (ListNode *)malloc(sizeof(ListNode));
    head->next->next->val = 3;
    head->next->next->next = (ListNode *)malloc(sizeof(ListNode));
    head->next->next->next->val = 2;
    head->next->next->next->next = (ListNode *)malloc(sizeof(ListNode));
    head->next->next->next->next->val = 5;
    head->next->next->next->next->next = NULL;

    int x = 3;

    ListNode *res = partition(head, x);

    while (res != NULL) {
        printf("%d ", res->val);
        res = res->next;
    }
    printf("\n");

    return 0;
}

这是一个简单的链表分割程序，使用dummy节点分别保存小于x和大于等于x的节点，然后将它们连接起来，并返回分割后的链表的头节点即可。