interviews/leetcode/two-pointers/LinkedListCycle.java at master · codingOnGithub/interviews

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

//Follow up:

//Can you solve it without using extra space?

/**

* 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 fast = head.next;

while(fast != null && fast.next != null && fast != slow) {

slow = slow.next;

fast = fast.next.next;

}

return fast == slow;

}