排序两个排序的链表----递归非递归实现

 ListNode* Merge1(ListNode* pHead1, ListNode* pHead2)
 {
     if(pHead1 == NULL)
         return pHead2;
     else if(pHead2 == NULL)
         return pHead1;
     
     ListNode* pMergedHead = NULL;
     
     if(pHead1->m_nValue < pHead2->m_nValue)
     {
         pMergedHead = pHead1;
         pMergedHead->m_pNext = Merge1(pHead1->m_pNext, pHead2);
     }
     else
      {
         pMergedHead = pHead2;
         pMergedHead->m_pNext = Merge1(pHead1, pHead2->m_pNext);
      }
     
     return pMergedHead;
 }

 

   ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
    {
      if(pHead1 == NULL)
         return pHead2;
      if(pHead2 == NULL)
          return pHead1;
 
      ListNode* NewHead=NULL;
        ListNode* temp=NULL;
        ListNode* pNode1 = pHead1;
        ListNode* pNode2 = pHead2;
        while(pNode1!=NULL && pNode2!=NULL)
        {
            if(NewHead==NULL)
            {
                if(pNode1->val <= pNode2->val)
                {
                    NewHead =pNode1;
                    pNode1 = pNode1->next;
                }
                else
                {
                    NewHead =pNode2;
                    pNode2 = pNode2->next;
                }
                temp=NewHead;
            }
            else
            {
                if(pNode1->val <= pNode2->val)
                {
                    temp->next=pNode1;
                    pNode1=pNode1->next;
                    //temp->next=NULL;
                    temp=temp->next;
                }
                else 
                {
                    temp->next=pNode2;
                    pNode2=pNode2->next;
                    //temp->next=NULL;
                    temp=temp->next;
                }
            }
 
        }
        if(pNode1==NULL && pNode2!=NULL)
            temp->next=pNode2;
        else if(pNode2==NULL && pNode1!=NULL)
            temp->next=pNode1; 
            
        return NewHead;
    }