LeetCode141 環形鏈表

環形鏈表>>>

雙指針：快慢指針

/**
 * Definition for singly-linked list.
 * class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public boolean hasCycle(ListNode head) {
        
        if(head==null||head.next==null) return false;

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