LeetCode : Merge Two Sorted Lists [java]

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.

思路：归并排序。

/** * 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) {        if(l1 == null){            return l2;        }        if(l2 == null){            return l1;        }ListNode head = null;ListNode p = null;if (l1.val < l2.val) {head = l1;p = head;l1 = l1.next;} else {head = l2;p = head;l2 = l2.next;}while (l1 != null && l2 != null) {if (l1.val < l2.val) {p.next = l1;p = p.next;l1 = l1.next;} else {p.next = l2;p = p.next;l2 = l2.next;}}while (l1 != null) {p.next = l1;p = p.next;l1 = l1.next;}while (l2 != null) {p.next = l2;p = p.next;l2 = l2.next;}return head;    }}