环形链表 循环 快慢指针 - lifengyu360/lifengyu_first_git_test GitHub Wiki

class Solution {

public:

bool hasCycle(ListNode *head) {
    if ((head == NULL) || (head->next== NULL)){
        return false;
    }
    ListNode *slow = head;
    ListNode *quick = head->next;
    while(slow != quick){
        if ((slow == NULL) ||(quick==NULL)|| (quick->next == NULL)){
            return false;
        }
        slow = slow->next;
        quick=quick->next->next;
    }
    return true;
}

};