# (LeetCode) 141. Linked List Cycle

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• 난이도 : Easy

### Problem

Given head, the head of a linked list, determine if the linked list has a cycle in it.

There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer. Internally, pos is used to denote the index of the node that tail’s next pointer is connected to. Note that pos is not passed as a parameter.

Return true if there is a cycle in the linked list. Otherwise, return false.

#### Constraints

• The number of the nodes in the list is in the range [0, 10^4].
• -10^5 <= Node.val <= 10^5
• pos is -1 or a valid index in the linked-list.

Exapnder

### Solution 2 - Next Pointer

Exapnder

#### Point of Thinking

• Set에 모든 노드의 val을 넣고 검증하는 전통적인 방법.
• next pointer를 이용해 비교해나가면서 순회하는 공간복잡도 최적의 방법.