每天一道LeetCode--141.Linked List Cycle（連結串列環問題）

Given a linked list, determine if it has a cycle in it.

Follow up:
Can you solve it without using extra space?

 參考部落格：連結串列環狀檢測

　　　　　　

package cn.magicdu;

import cn.magicdu.extra.ListNode;

public class _114_Linked_List_Cycle {
    public boolean hasCycle(ListNode head) {
        ListNode fast = head, slow = head;

        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
            if (slow == fast) {
                return true;
            }
        }
        return false;

    }
}