LeetCode 21 Merge Two Sorted Lists

题目：

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.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

解答：

最基本的合并排序

/**
 * 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 head = new ListNode(-1);
        ListNode p = head;
        
        while(l1!=null&&l2!=null)
        {
            if(l1.val<=l2.val)
            {
                p.next = l1;
                l1=l1.next;
            }
            else
            {
                p.next = l2;
                l2=l2.next;
            }
            p = p.next;
        }
        
        if(l1!=null)
            p.next = l1;
        if(l2!=null)
            p.next = l2;
        return head.next;
        
        
    }
}