A small trick :)

Author: viewv

141. Linked List Cycle.py

@@ -0,0 +1,22 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+
+class Solution(object):
+    def hasCycle(self, head):
+        """
+        :type head: ListNode
+        :rtype: bool
+        """
+        while head != None:
+            if head.next == None:
+                return False
+            elif head.next.val == "!":
+                return True
+            else:
+                head.val = "!"
+                head = head.next
+        return False