将两个非递减单链表合并成一个有序的非递减单链表的c语言代码

下面是将两个非递减单链表合并成一个有序的非递减单链表的c语言代码：

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

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

ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
    ListNode* head = (ListNode*)malloc(sizeof(ListNode));
    ListNode* cur = head;

    while (l1 != NULL && l2 != NULL) {
        if (l1->val <= l2->val) {
            cur->next = l1;
            l1 = l1->next;
        } else {
            cur->next = l2;
            l2 = l2->next;
        }
        cur = cur->next;
    }

    if (l1 != NULL) {
        cur->next = l1;
    }

    if (l2 != NULL) {
        cur->next = l2;
    }

    return head->next;
}

int main() {
    // test case
    ListNode* l1 = (ListNode*)malloc(sizeof(ListNode));
    l1->val = 1;
    l1->next = (ListNode*)malloc(sizeof(ListNode));
    l1->next->val = 3;
    l1->next->next = (ListNode*)malloc(sizeof(ListNode));
    l1->next->next->val = 5;
    l1->next->next->next = NULL;

    ListNode* l2 = (ListNode*)malloc(sizeof(ListNode));
    l2->val = 2;
    l2->next = (ListNode*)malloc(sizeof(ListNode));
    l2->next->val = 4;
    l2->next->next = (ListNode*)malloc(sizeof(ListNode));
    l2->next->next->val = 6;
    l2->next->next->next = NULL;

    ListNode* mergedList = mergeTwoLists(l1, l2);

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

    return 0;
}

这段代码可以将两个非递减单链表合并成一个有序的非递减单链表。具体实现是先创建一个空的头结点，然后遍历两个链表，每次将较小的节点加入到新链表中即可。最后需要注意的是，返回结果应该是头结点的下一个节点。