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.

题意：合并两个已经排序好的链表。

代码：

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