合并两个排序的链表

题目:输入两个递增排序的链表，合并这两个链表并使新链表中的结点仍然是按照递增排序的。链表结点定义如下:

struct ListNode{
	int m_nValue;
	int m_pNext;
};

//利用递归
ListNode *Merge(ListNode *phead1, ListNode *phead2)
{
	if (phead1==NULL)
	    return phead2;
	else if (phead2==NULL)
		return phead1;
	//新链表的头指针
	ListNode *pNewHead=NULL;
	if (phead1->m_nValue<phead2->m_nValue)
	{
		pNewHead=phead1;
		pNewHead->m_pNext=Merge(phead1->m_pNext,phead2);
	}
	else
	{
		pNewHead=phead2;
        pNewHead->m_pNext=Merge(phead1,phead2->m_pNext);
	}
	return pNewHead;
}