LC-0141 Easy LeetCode

141. Linked List Cycle

Hash Table Linked List Two Pointers

Read the full problem statement on LeetCode.

Difficulty: easy Acceptance: 52% Topics: Hash Table, Linked List, Two Pointers

View full problem on LeetCode

Also on leetcode.ca (community mirror)

Reading material

Arrays & Hashing 12 min Linked Lists 14 min Two Pointers 9 min

Reference solution (spoiler · python)

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None


class Solution:
    def hasCycle(self, head: ListNode) -> bool:
        if not head or not head.next:
            return False

        slow = head
        fast = head.next

        while slow != fast:
            if not fast or not fast.next:
                return False
            slow = slow.next
            fast = fast.next.next

        return True

Solution from kamyu104/LeetCode-Solutions · MIT