函数：

1 ListNode* MeetingNode(ListNode* pHead) 2 { 3     if(pHead==nullptr) 4         return nullptr; 5     ListNode* quickNode=pHead; 6     ListNode* slowNode=pHead; 7  8     while(quickNode->m_pNext!=nullptr&&quickNode->m_pNext->m_pNext!=nullptr) 9     {10         quickNode=quickNode->m_pNext->m_pNext;11         slowNode=slowNode->m_pNext;12         if(quickNode==slowNode)13             break;14     }15     if(quickNode!=slowNode)16     {17         return nullptr;18     }19     return slowNode;20 }21 22 ListNode* EntryNodeOfLoop(ListNode* pHead)23 {24     ListNode* meetingNode=MeetingNode(pHead);25     if(meetingNode==nullptr)26         return nullptr;27     int nodesInLoop=1;28     ListNode* pTemp=meetingNode;29     while(pTemp->m_pNext!=meetingNode)30     {31         pTemp=pTemp->m_pNext;32         nodesInLoop++;33     }34     ListNode* quickNode=pHead;35     ListNode* slowNode=pHead;36     for(int i=0;i
      
       m_pNext;38     while(slowNode!=quickNode)39     {40         quickNode=quickNode->m_pNext;41         slowNode=slowNode->m_pNext;42     }43     return slowNode;44 }
      

测试代码：

1 #include"List.h" 2  3 void Test(char* testName,ListNode* pHead,ListNode* expect) 4 { 5     cout<
      
       <<":"; 6     ListNode* result=EntryNodeOfLoop(pHead); 7     if(result==nullptr) 8     { 9         cout<<"No loop in the link list."<
      

主要要销毁所定义的指针变量和链表。如果链表中存在环，则可以一个个节点去释放。