标签:head Linked list List next cycle twoStep linked Cycle
Given a linked list, determine if it has a cycle in it.
To represent a cycle in the given linked list, we use an integer pos
which represents the position (0-indexed) in the linked list where tail connects to. If pos
is -1
, then there is no cycle in the linked list.
Example 1:
Input: head = [3,2,0,-4], pos = 1 Output: true Explanation: There is a cycle in the linked list, where tail connects to the second node.
Example 2:
Input: head = [1,2], pos = 0 Output: true Explanation: There is a cycle in the linked list, where tail connects to the first node.
Example 3:
Input: head = [1], pos = -1 Output: false Explanation: There is no cycle in the linked list.
Follow up:
Can you solve it using O(1) (i.e. constant) memory?
空间复杂度O(n)
public boolean hasCycle(ListNode head) {//链表 Set<ListNode> nodeSet = new HashSet<ListNode>(); while(null!= head){ if(nodeSet.contains(head)){ return true; } else{ nodeSet.add(head); head=head.next; } } return false; }
空间复杂度O(1)
public boolean hasCycle(ListNode head) {//链表 mytip ListNode oneStep = head; ListNode twoStep =head; while(null!=oneStep){ oneStep=oneStep.next; if(null==twoStep.next||null==twoStep.next.next){ return false; } twoStep=twoStep.next.next; if (oneStep==twoStep){ return true; } } return false; }
标签:head,Linked,list,List,next,cycle,twoStep,linked,Cycle 来源: https://www.cnblogs.com/zhacai/p/10560803.html
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