合并两个排序的链表

题目：输入两个递增的排序的链表，合并这两个链表并使新链表中的节点仍然是按照递增顺序的。链表的结构如下：

struct ListNode{

　　　　int m_nValue;

　　　　ListNode* m_pNext;

　　}

 1 struct ListNode{
 2     int m_nValue;
 3     ListNode* m_pNext;
 4 }
 5 
 6 ListNode* Merge(ListNode* pHead1,ListNode* pHead2){
 7     if(pHead1 == NULL)
 8         return pHead2;
 9     else if(pHead2 == NULL)
10         return pHead1;
11 
12     ListNode* pHead3 = NULL;
13     if(pHead1->m_nValue < pHead2->m_nValue){
14         pHead3 = pHead1;
15         pHead3->m_pNext = Merge(pHead1->m_pNext,pHead2);
16     }else{
17         pHead3 = pHead2;
18         pHead3->m_pNext = Merge(pHead1,pHead2->m_pNext);
19     }
20     return pHead3;
21 }