用C语言写出两个链表按大小顺序合并

下面是用C语言实现的两个链表按大小顺序合并的示例代码：

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

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

// 创建新的链表节点
struct ListNode* createNode(int val) {
    struct ListNode* node = (struct ListNode*)malloc(sizeof(struct ListNode));
    node->val = val;
    node->next = NULL;
    return node;
}

// 合并两个有序链表
struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) {
    if (l1 == NULL) return l2;
    if (l2 == NULL) return l1;
    struct ListNode* head = NULL;
    struct ListNode* tail = NULL;
    while (l1 && l2) {
        if (l1->val < l2->val) {
            if (head == NULL) {
                head = tail = l1;
            } else {
                tail->next = l1;
                tail = l1;
            }
            l1 = l1->next;
        } else {
            if (head == NULL) {
                head = tail = l2;
            } else {
                tail->next = l2;
                tail = l2;
            }
            l2 = l2->next;
        }
    }
    if (l1) tail->next = l1;
    if (l2) tail->next = l2;
    return head;
}

int main() {
    // 创建两个有序链表
    struct ListNode* l1 = createNode(1);
    l1->next = createNode(3);
    l1->next->next = createNode(5);
    struct ListNode* l2 = createNode(2);
    l2->next = createNode(4);
    l2->next->next = createNode(6);
    l2->next->next->next = createNode(8);

    // 合并两个有序链表
    struct ListNode* mergedList = mergeTwoLists(l1, l2);

    // 输出合并后的链表
    while (mergedList) {
        printf("%d ", mergedList->val);
        mergedList = mergedList->next;
    }
    printf("\n");

    return 0;
}

输出结果为：1 2 3 4 5 6 8