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; } * } */class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        ListNode dummy = new ListNode(0);        ListNode node = dummy;        while(l1 != null && l2 != null) {            if (l1.val < l2.val) {                node.next = l1;                l1 = l1.next;            }            else {                node.next = l2;                l2 = l2.next;            }            node = node.next;        }        if (l1 != null) {            node.next = l1;        }        else {            node.next = l2;        }        return dummy.next;    }}