Problem

Merge two sorted (ascending) linked lists and return it as a new sorted list. The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.

Example

Given 1->3->8->11->15->null, 2->null, return 1->2->3->8->11->15->null.

Note

先考虑l1和l2有无空集，有则返回另一个。

Solution

public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        if (l1 == null) return l2;        if (l2 == null) return l1;        ListNode dummy = new ListNode(0), 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;        if (l2 != null) node.next = l2;        return dummy.next;    }}