题目描述
一个链表中包含环，请找出该链表的环的入口结点。
/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};
*/
class Solution {
public:
ListNode* EntryNodeOfLoop(ListNode* pHead)
{
ListNode* fast = pHead;
ListNode* slow = pHead;
while(fast != NULL && fast->next != NULL){
fast = fast->next->next;
slow = slow->next;
if(fast == slow)
break;
}
if(fast == NULL || fast->next == NULL)
return NULL;
fast = pHead;
while(fast != slow){
fast = fast->next;
slow = slow->next;
}
return slow;
}
};
