Merge two sorted linked lists - two questions per day

The finger of the sword Offer 25. Merge two ordered linked lists

Brushing questions makes me happy , The following question must be very simple . It must be too easy for you to say after reading

Take it Ha ha ha ha ha ha ha

Enter two ascending ordered linked lists , Merge these two linked lists and make the nodes in the new linked list still be sorted incrementally ..

Example 1：

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

Limit ：

0 <=  Chain length  <= 1000

Ideas

Create a new virtual node , Let the two nodes be spliced separately , The rule of splicing is , Look who is small Whoever is with Virtual head nodes form a linked list Splicing

After the final spelling , Certainly at most one linked list is not null , Why not null , Direct splicing , Finished , The ease with which , Look at the code

class Solution {
    
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    
                    ListNode left=l1;
        ListNode right=l2;
        ListNode newNode=new ListNode(-1);
        ListNode cur=newNode;
        while (left!=null&& right!=null){
    
            if (left.val<= right.val){
    
                cur.next=left;
                left=left.next;
            }else {
    
                cur.next=right;
                right=right.next;
            }
             cur=cur.next;
        }

       if (right!=null){
    
            cur.next=right;
        }
        if (left!=null){
    
            cur.next=left;
        }
        return newNode.next;
   }
}