题解 | #链表中环的入口结点#

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
        val(x), next(NULL) {
    }
};
*/
class Solution {
public:
    ListNode* EntryNodeOfLoop(ListNode* pHead) {
        ListNode *pre = pHead, *temp;
        while(pre){
            if(pre->next==pre)
                return pre->next;
            temp = pre;
            pre = pre->next;
            temp->next = temp;
        }
        return NULL;
    }
};