21. 合并两个排序单链表 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.

创建一个新结点，同时遍历两个链表，取较小的一个添加到新结点后面。

最后再把剩下的节点加到链表后面

public class Solution {
    public ListNode MergeTwoLists(ListNode l1, ListNode l2) {
        ListNode curNode = null;
        ListNode headNode = new ListNode(-1);
        curNode = headNode;
        while (l1 != null && l2 != null)
        {
            if (l1.val < l2.val)
            {
                curNode.next = l1;
                l1 = l1.next;
            }
            else
            {
                curNode.next = l2;
                l2 = l2.next;
            }
            curNode = curNode.next;
        }
        if (l2 != null)
        {
            curNode.next = l2;
        }
        else if (l1 != null)
        {
            curNode.next = l1;
        }
        return headNode.next;
    }
}

null