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
    struct ListNode *fast = head ;//快指针--先走两步
    struct ListNode *slow = head ; //慢指针
    while (fast) {
        fast = fast->next;
        if(fast == NULL)
            break;
        fast = fast->next ;
        slow = slow->next;
        if(fast == slow) //有环
            return true;
    }
    return false;
}