[Leetcode]-Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
题目：合并两个排序后的单链表，要求合并之后也是排序好的
思路：递归合并

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next; 
 * };
 */
struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) {
    if(NULL == l1) return l2;
    if(NULL == l2) return l1;

    struct ListNode* MergeList = NULL;

    if(l1->val < l2->val)
    {
        MergeList = l1;
        MergeList->next = mergeTwoLists(l1->next,l2);
    }

    else
    {
        MergeList = l2;
        MergeList->next = mergeTwoLists(l1,l2->next);
    }


    return MergeList;
}