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 ) {
    //思路
    //使用快慢指针，若二者相遇，则表示有环

    struct ListNode* fast = head;
    struct ListNode* slow = head;

    if (head == NULL) {
        return false;
    }

    while ((slow != NULL) && (fast != NULL) && (fast->next != NULL)) {
        slow = slow->next;
        fast = fast->next->next;
        if (slow == fast) {
            return true;
        }
    }
    return false;
}