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) {
        // 设置快慢指针
        ListNode* slow=head;
        ListNode* fast=head;
        while(slow && fast) {
            slow = slow->next;
            if(fast->next) fast = fast->next->next;
            else return false;
            // 当双指针相遇 即表示指针有环
            if(slow == fast) return true;
        }
        return false;
    }
};