update linked list questions

Author: KaidiGuo

Linked List/141. Linked List Cycle.py

@@ -0,0 +1,18 @@
+# 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:
+        visited={}
+        while head:
+            if head in visited.keys():
+                print("visited")
+                return True
+            else:
+                visited[head]=1
+                head = head.next
+                
+        return False