21. Merge Two Sorted Lists

题目

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.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

分析

1 很早之前做过类似的合并

2 分为两步  1 while循环里判断此次结点的下一个结点应该指向谁

                 2 最后再接上仍然存在结点的链表

3 注意一开始仍然要用dummy 存一下， Newstart在一直变化

代码

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
         ListNode newStart = new ListNode(0);
        ListNode dummy = newStart;
        while (l1!= null && l2 != null){
            if(l1.val > l2.val){
                newStart.next = l2;
                l2 = l2.next;
            }else {
                newStart.next = l1;
                l1 = l1.next;
            }
            newStart = newStart.next;
            
        }
        newStart.next = l1 == null ? l2 : l1;
        return dummy.next;
    }