21. Merge Two Sorted Lists

题目描述

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.

解题方法

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        //Using one dummy node as start pointer 
        ListNode dummy = new ListNode(0);
        ListNode lastNode = dummy;

        //Merging l1 and l2 until one of them is end
        while( l1 != null && l2 != null){
            if( l1.val <= l2.val ){
                lastNode.next = l1;
                l1= l1.next;
            }else{
                lastNode.next = l2;
                l2= l2.next;
            }
            lastNode = lastNode.next;
        }

        //Mearging the rest LinkedList
        if(l1 != null){
            lastNode.next = l1;
        }else{
            lastNode.next = l2;
        }

        return dummy.next;
    }