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0141-linked-list-cycle.adoc

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141. Linked List Cycle

{leetcode}/problems/linked-list-cycle/[LeetCode - Linked List 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.
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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.
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Example 3:

Input: head = [1], pos = -1
Output: false
Explanation: There is no cycle in the linked list.
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Follow up:

Can you solve it using O(1) (i.e. constant) memory?

思路分析

除了双指针外，还可以使用 Map 来解决。只是空间复杂度要高一些。

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link:{sourcedir}/_0141_LinkedListCycle.java[role=include]
link:{sourcedir}/_0141_LinkedListCycle_2.java[role=include]