c_cpp 141.关联名单周期

Posted 2021-05-14

//Runtime: 16 ms, faster than 7.06% 

class Solution {
public:
    bool hasCycle(ListNode *head) {
        if(!head || !head->next ) return false;
        
        set<ListNode *> array;
        
        while(head->next != NULL){
            head = head->next;
            array.insert(head);
            if(array.count(head->next))
                return true;
        }
        return false;
    }
};

//Runtime: 8 ms, faster than 66.59%

class Solution {
public:
    bool hasCycle(ListNode *head) {
        ListNode *fast = head;
        ListNode *slow = head;
        
        while(fast && fast->next){
            slow = slow->next;
            fast = fast->next->next;
            
            if(fast == slow)
                return true;
        }
        return false;
    }
};