leetcode141环形链表

给定一个链表，判断链表中是否有环。

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */

//快慢指针
bool hasCycle(struct ListNode *head) {
    struct ListNode *p1 =head;
    struct ListNode *p2 = head;
   
    while(1)
    {
        if(p1 == NULL)
        {
            return false;
        }
        p1 = p1->next;
        if(p1 == NULL)
        {
            return false;
        }
        p1 = p1->next;
        
        p2 = p2->next;
        
        if(p1 != NULL && p1 == p2 )
        {
            return 1;
        }
    }

}