LeetCode 21. 合并两个有序链表

原题网址：https://leetcode.cn/problems/merge-two-sorted-lists/submissions/

合并两个排好序的链表；遍历节点；小的当新节点的值；之后后移；在比较；

    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
    
        ListNode l1 = list1;
        ListNode l2 = list2;
        ListNode dummyHead = new ListNode(-1);
        ListNode node = dummyHead;
        while( l1 != null && l2 != null) {
    
            ListNode newNode = null;
            if(l1.val <l2.val) {
    
                newNode = new ListNode(l1.val);
                l1 = l1.next;
            } else {
    
                newNode = new ListNode(l2.val);
                l2 = l2.next;
            }

         
            node.next = newNode;
            node = newNode;
        }
        if(l1 != null) {
    
            node.next = l1;
        }
        if(l2 != null) {
    
            node.next= l2;
        }
        return dummyHead.next;
            

    }