21. 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.

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        ListNode head = new ListNode(0);        ListNode l3 = head;                while(l1 != null && l2 != null)        {            if(l1.val <= l2.val)            {                l3.next = l1;                l1 = l1.next;            }            else            {                l3.next = l2;                l2 = l2.next;            }            l3 = l3.next;        }                if(l1 != null)            l3.next = l1;                    if(l2 != null)            l3.next = l2;       return head.next;    }}