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) {
        if (pHead == nullptr) {
            return nullptr;
        }
        vector<ListNode*> link;
        link.push_back(pHead);
        ListNode* p = pHead->next;
        while (p != nullptr) {
            for (auto& i : link) {
                if (i == p) {
                    return p;
                }
            }
            link.push_back(p);
            p = p->next;
        }
        return nullptr;
    }
};