linked-list-cycle solution

Author: devyejin

linked-list-cycle/devyejin.py

@@ -0,0 +1,35 @@
+# Definition for singly-linked list.
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+from typing import Optional
+
+# time complexity O(n)
+# space complexity O(1)
+class Solution:
+    def hasCycle(self, head: Optional[ListNode]) -> bool:
+        slow, fast = head, head
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+
+            if slow == fast:
+                return True
+        return False
+
+
+# time complexity O(n)
+# space complexity O(n)
+# class Solution:
+#     def hasCycle(self, head: Optional[ListNode]) -> bool:
+#         visited = set()
+#         while head:
+#             if head in visited:
+#                 return True
+#             visited.add(head)
+#             head = head.next
+#         return False
+
+