c_cpp 141.链表循环 - 简易 - 2018.7.30

Posted 2021-05-14

/**
1：两个指针，slowPointer 每次步进 1，fastPointer 每次步进 2
2：如果快指针到尽头了，说明没有循环
3：如果两个指针最后碰头了，说明存在一个循环
 */
 
class Solution {
public:
    bool hasCycle(ListNode *head) {
        ListNode *slow = head, *fast = head;
        while (fast && fast->next) {
            slow = slow->next;
            fast = fast->next->next;
            if (slow == fast) return true;
        }
        return false;
    }
};