#141. Linked List Cycle | LeetCode Python Solution

Problem

LeetCode Problem

141. Linked List Cycle

Python Solution

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

class Solution:
    def hasCycle(self, head: Optional[ListNode]) -> bool:
        # No cycle if the list is empty
        if head is None:
            return False

        # Use a set to keep track of memory location of visited nodes
        node_set = set()

        c = head
        while c.next is not None:
            # Cycle detected if the 'next' pointer references the memory location of visited nodes
            if c.next in node_set:
                return True

            # Add current node's memory location to the set
            node_set.add(c)

            # Advance current pointer to next node
            c = c.next

        # Reached the end of the given linked list without detecting any cycle
        return False