Created linkedlist_hasCycle.py

DS&Algo Programs in Python/linkedlist_hasCycle.py

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+from typing import Optional
+
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None   
+
+class Solution:
+    def hasCycle(self,head:Optional[ListNode])->bool:
+
+        #if no linkedlist or a single node linkedlist
+        if head is None or head.next is None:
+            return False
+
+        slow=head
+        fast=head
+
+        while slow!=fast:
+            if fast is None or fast.next is None:
+                return False
+
+            slow=slow.next #goes to next node
+            fast=fast.next.next #goes to next to next node
+
+        return True
+
+# Create some nodes for a linked list
+node1 = ListNode(1)
+node2 = ListNode(2)
+node3 = ListNode(3)
+node4 = ListNode(4)
+node5 = ListNode(5)
+node6 = ListNode(6)
+node7 = ListNode(7)
+
+# Link the nodes together
+node1.next = node2
+node2.next = node3
+node3.next = node4
+node4.next = node5
+node5.next = node6
+node6.next = node7
+
+# Optionally create a cycle
+# Uncomment the line below to create a cycle
+node6.next = node3
+
+# Create an instance of the Solution class
+solution = Solution()
+
+# Check if the linked list has a cycle
+result = solution.hasCycle(node1)
+
+# Print the result
+print("Cycle detected!" if result else "No cycle detected")