判断带环链表相交的点

1、判断两个链表是否相交，若相交，求交点。（假设链表可能带环）。

#include<iostream>#include<assert.h>using namespace std;struct ListNode{int _value;ListNode* _next;ListNode(int value):_value(value), _next(NULL){}};ListNode* IsCircleList(ListNode* pHead)//是否带环，返回快慢节点相交的节点{if (pHead == NULL)return NULL;ListNode* pFast = pHead;ListNode* pSlow = pHead;while (pFast && pFast->_next){pFast = pFast->_next->_next;pSlow = pSlow->_next;if (pFast == pSlow)return pSlow;}return NULL;}int Size(ListNode* pHead){ListNode* pLast = pHead;int count = 1;while (pLast->_next){count++;pLast = pLast->_next;}return count;}bool IsCrossList(ListNode* pHead1, ListNode* pHead2)//判断两个链表是否相交{if (pHead1 == NULL || pHead2 == NULL)return true;ListNode* pCur1 = pHead1;ListNode* pCur2 = pHead2;while (pCur1->_next)pCur1 = pCur1->_next;while (pCur2->_next)pCur2 = pCur2->_next;if (pCur1 == pCur2)return true;return false;}ListNode* CrossNode(ListNode* pHead)//判断入环节点{if (pHead == NULL)return NULL;ListNode* pNode = pHead;ListNode* pMeet = IsCircleList(pHead);if (pMeet == NULL)//链表不带环return NULL;//链表带环while (pNode != pMeet){pNode = pNode->_next;pMeet = pMeet->_next;}return pNode;}//判断两个链表的相交点，两个带环int Number(ListNode* pHead, ListNode* pNode){if (pHead == NULL || pNode == NULL)return 0;ListNode* pCurNode = pHead;int count = 1;while (pCurNode != pNode){count++;pCurNode = pCurNode->_next;}return count;}ListNode* CircleListNode(ListNode* pHead1, ListNode* pHead2)//判断两个链表的相交点，两个带环{if (pHead1 == NULL && pHead2 == NULL)return NULL;ListNode* pCircleNode1 = IsCircleList(pHead1);//链表1环的节点ListNode* pCircleNode2 = IsCircleList(pHead2);//链表2环的节点if (pCircleNode1 == NULL && pCircleNode2 == NULL)//两个链表都不带环{if (IsCrossList(pHead1, pHead2))//两个链表相交{int count = Size(pHead1) - Size(pHead2);ListNode* pStrNode = pHead1;ListNode* pStyNode = pHead2;if (count > 0){while (count--)pStrNode = pStrNode->_next;}else{count = 0 - count;while (count--)pStyNode = pStyNode->_next;}while (pStrNode != pStyNode){pStrNode = pStrNode->_next;pStyNode = pStyNode->_next;}return pStrNode;}elsereturn NULL;}//两个链表都带环else if (pCircleNode1 && pCircleNode2){ListNode* pCrossNode1 = CrossNode(pHead1);//链表1的入环节点ListNode* pCrossNode2 = CrossNode(pHead2); //链表2的入环节点ListNode* pCtrNode = pHead1;ListNode* pCtyNode = pHead2;if (pCrossNode1 == pCrossNode2)//两个链表从一个节点入环，则相交在这个节点之前或者这个节点{int number = Number(pHead1, pCrossNode1) - Number(pHead2, pCrossNode2);if (number > 0){while (number--)pCtrNode = pCtrNode->_next;}else{number = 0 - number;while (number--)pCtyNode = pCtyNode->_next;}while (pCtrNode != pCtyNode){pCtrNode = pCtrNode->_next;pCtyNode = pCtyNode->_next;}return pCtrNode;}//相交点在环内，在一个环内找一个点，在另一个环内找到就有相交点，没找到就没相交点ListNode *pCurNode = pCircleNode1;while (pCircleNode1 != pCurNode->_next)//最后一个节点没遍历{if (pCurNode == pCircleNode2)return pCurNode;pCurNode = pCurNode->_next;}if (pCircleNode2 == pCurNode)return pCurNode;}//一个带环，一个不带环永远不可能相交return NULL;}void printfList(ListNode* pHead){while (pHead){cout << pHead->_value << " ";pHead = pHead->_next;}cout << endl;}void Funtest(){ListNode* pHead1 = new ListNode(1);ListNode* pNode = pHead1;for (int idx = 3; idx <= 20; idx += 2){pNode->_next = new ListNode(idx);pNode = pNode->_next;}printfList(pHead1);ListNode* pHead2 = new ListNode(2);ListNode* pTemp = pHead2;for (int idx = 4; idx <= 20; idx += 2){pTemp->_next = new ListNode(idx);pTemp = pTemp->_next;}printfList(pHead2);//pTemp->_next = pHead1->_next;//判断两个链表是相交cout << "链表是否相交：" << IsCrossList(pHead1, pHead2) << endl;//*****************************************************************//判断链表是否带环pNode->_next = pHead1->_next->_next->_next;ListNode* pCircle1 = IsCircleList(pHead1);//判断带环链表的快慢指针相交点if (pCircle1)cout << "链表1带环相交节点：" << pCircle1->_value << endl;elsecout << "链表1不带环！" << endl;//pTemp->_next = pHead2->_next->_next;pTemp->_next = pHead1->_next->_next->_next->_next;ListNode* pCircle2 = IsCircleList(pHead2);if (pCircle2)cout << "链表2带环相交节点：" << pCircle2->_value << endl;elsecout << "链表2不带环！" << endl;//找出链表带环的入环节点ListNode* pCross1 = CrossNode(pHead1);if (pCross1)cout <<"链表1入环节点："<<pCross1->_value << endl;elsecout << "链表1不带环！" << endl;ListNode* pCross2 = CrossNode(pHead2);if (pCross2)cout << "链表2入环节点：" << pCross2->_value << endl;elsecout << "链表2不带环！" << endl;//判断两个带坏链表的相交点ListNode* pCircleNode = CircleListNode(pHead1, pHead2);if (pCircleNode)cout << "相交点：" << pCircleNode->_value << endl;elsecout << "链表不相交！" << endl;}