题解 | #判断链表中是否有环#

#include <stdbool.h>
/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

/**
 * 
 * @param head ListNode类 
 * @return bool布尔型
 */
bool hasCycle(struct ListNode* head ) {
    // write code here
    if(head == NULL)
    {
        return false;
    }

    struct ListNode* slow = head;//慢指针
    struct ListNode* fast = head;//快指针
    while(fast!=NULL && fast->next!=NULL)
    {
        slow = slow->next;//走一步
        fast = fast->next->next;//走两步
        if(slow == fast)//判断是否有环
        {
            return true;
        }
    }

    return false;

}