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) {}
 * };
 */
class Solution {
public:
    bool hasCycle(ListNode *head) {
        ListNode*p,*pp;
        p = pp = head;
        
        while(pp)
        {
            p=p->next;
            pp=pp->next;
            if(pp) pp = pp->next;
            if(p==pp&&p!=nullptr)
            {
                return true;
            }
        }
        return false;
        
    }
};

两个指针不同步走的经典例题