用c语言写一个非递增的两个单链表的合并

可以使用以下代码实现：

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

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

Node* merge(Node* l1, Node* l2) {
    Node dummy;
    Node* tail = &dummy;
    while (l1 && l2) {
        if (l1->val >= l2->val) {
            tail->next = l1;
            l1 = l1->next;
        } else {
            tail->next = l2;
            l2 = l2->next;
        }
        tail = tail->next;
    }
    tail->next = l1 ? l1 : l2;
    return dummy.next;
}

int main() {
    Node* l1 = (Node*)malloc(sizeof(Node));
    l1->val = 3;
    l1->next = (Node*)malloc(sizeof(Node));
    l1->next->val = 2;
    l1->next->next = (Node*)malloc(sizeof(Node));
    l1->next->next->val = 1;
    l1->next->next->next = NULL;

    Node* l2 = (Node*)malloc(sizeof(Node));
    l2->val = 4;
    l2->next = (Node*)malloc(sizeof(Node));
    l2->next->val = 2;
    l2->next->next = (Node*)malloc(sizeof(Node));
    l2->next->next->val = 1;
    l2->next->next->next = NULL;

    Node* merged = merge(l1, l2);
    while (merged) {
        printf("%d ", merged->val);
        merged = merged->next;
    }
    printf("\n");

    return 0;
}

这个程序会创建两个单链表 `l1` 和 `l2`，然后调用 `merge` 函数将它们合并成一个非递增的单链表，并输出结果。