Linked List Cycle
47% Accepted
Given a linked list, determine if it has a cycle in it.
Example
Given -21->10->4->5, tail connects to node index 1, return true
Challenge
- Can you solve it without using extra space?
Tags Expand
- Two Pointers
- Linked List
思路
- 快慢指针,如果相遇,说明有环
/**
* Definition for ListNode.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int val) {
* this.val = val;
* this.next = null;
* }
* }
*/
public class Solution {
/**
* @param head: The first node of linked list.
* @return: True if it has a cycle, or false
*/
public boolean hasCycle(ListNode head) {
// write your code here
if (head == null) {
return false;
}
ListNode fast = head;
ListNode slow = head;
while (fast != null && fast.next != null) {
fast = fast.next.next;
slow = slow.next;
if (fast == slow) {
return true;
}
}
return false;
}
}