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LinkedListCycle.java
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LinkedListCycle.java
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package datastructure.linkedlist.leetcode;
import java.util.HashSet;
import java.util.Set;
/**
* @author roseduan
* @time 2020/10/24 2:25 下午
* @description 环形链表
*/
public class LinkedListCycle {
/**
* 使用一个set判重
*/
public boolean hasCycle1(ListNode head) {
Set<ListNode> set = new HashSet<>();
while (head != null) {
if (set.contains(head)) {
return true;
}
set.add(head);
head = head.next;
}
return false;
}
/**
* 快慢指针法
*/
public boolean hasCycle2(ListNode head) {
ListNode slow = head, fast = head;
while (fast != null && fast.next != null) {
slow = slow.next;
fast = fast.next.next;
if (slow == fast) {
return true;
}
}
return false;
}
public static class ListNode {
int val;
ListNode next;
ListNode() {}
ListNode(int val) { this.val = val; }
}
}