请用c语言编程实现有序链表合并。

好的，以下是有序链表合并的C语言代码：

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

struct node {
    int data;
    struct node* next;
};

struct node* merge(struct node* list1, struct node* list2) {
    struct node* result = NULL;
    struct node** tail = &result; 

    while (1) {
        if (list1 == NULL) {
            *tail = list2;
            break;
        } else if (list2 == NULL) {
            *tail = list1;
            break;
        }

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

    return result;
}

void printList(struct node* list) {
    while (list) {
        printf("%d ", list->data);
        list = list->next;
    }
    printf("\n");
}

int main() {
    struct node* list1 = NULL;
    struct node* list2 = NULL;

    list1 = (struct node*)malloc(sizeof(struct node));
    list1->data = 1;
    list1->next = (struct node*)malloc(sizeof(struct node));
    list1->next->data = 3;
    list1->next->next = (struct node*)malloc(sizeof(struct node));
    list1->next->next->data = 5;
    list1->next->next->next = NULL;

    list2 = (struct node*)malloc(sizeof(struct node));
    list2->data = 2;
    list2->next = (struct node*)malloc(sizeof(struct node));
    list2->next->data = 4;
    list2->next->next = (struct node*)malloc(sizeof(struct node));
    list2->next->next->data = 6;
    list2->next->next->next = NULL;

    printf("List 1: ");
    printList(list1);
    printf("List 2: ");
    printList(list2);

    struct node* mergedList = merge(list1, list2);
    printf("Merged list: ");
    printList(mergedList);

    return 0;
}

这里我使用了指针来操作链表，对于两个有序链表 `list1` 和 `list2`，我首先定义一个指向结果链表的指针 `tail`，然后使用循环比较 `list1` 和 `list2` 中的节点值大小，将较小的节点移动到 `tail` 指向的链表中，并更新 `tail` 指向较小值的节点。重复这个过程直到有一个链表被遍历完，最后将 `tail` 指向另一个链表的剩余部分，即得到了合并后的有序链表。

希望这段代码能帮到您！