将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 

示例：

输入：1->2->4, 1->3->4输出：1->1->2->3->4->4.

1 public class MergeTwoSortedLists {     2     private class ListNode { 3         int val;  4         ListNode next; 5          6         ListNode(int x) { 7             val = x; 8         } 9     }10     public ListNode mergeTwoLists(ListNode l1, ListNode l2) {11         if(l1 == null) {12             return l2;13         }14         if(l2 == null) {15             return l1;16         }17         ListNode result = new ListNode(0);18         ListNode curRes = result;19         ListNode curNode1 = l1;20         ListNode curNode2 = l2;21         while(curNode1 != null && curNode2 != null) {22             if(curNode1.val < curNode2.val) {23                 curRes.next = new ListNode(curNode1.val);24                 curNode1 = curNode1.next;25                 curRes = curRes.next;26             }else {27                 curRes = new ListNode(curNode2.val);28                 curNode2 = curNode2.next;29                 curRes = curRes.next;30             }31         }32 /*        while(curNode1 != null) {33             curRes.next = new ListNode(curNode1.val);34             curRes = curRes.next;35             curNode1 = curNode1.next;36         }37         38         while(curNode2 != null) {39             curRes.next = new ListNode(curNode2.val);40             curRes = curRes.next;41             curNode2 = curNode2.next;42         }*/43         //无需循环判断，其中一个为空，则将不为空的直接赋值即可44         if(curNode1 != null) {45             curRes.next = curNode1;46         }else {47             curRes.next = curNode2;48         }49         return result.next;50     }51 }