题解 | #判断链表中是否有环#

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
#include <vector>
class Solution {
  public:
    bool hasCycle(ListNode* head) {
        if (head == nullptr) {
            return false;
        }
        vector<ListNode*> link;
        link.push_back(head);
        ListNode* p = head->next;
        while (p != nullptr) {
            for (auto& i : link) {
                if (i == p) {
                    return true;
                }
            }
            link.push_back(p);
            p = p->next;
        }
        return false;
    }
};