Create Loop linked list

Loop linked list

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+# Python program to detect loop 
+# in the linked list 
+
+# Node class  
+class Node: 
+
+    # Constructor to initialize 
+    # the node object 
+    def __init__(self, data): 
+        self.data = data 
+        self.next = None
+
+class LinkedList: 
+
+    # Function to initialize head 
+    def __init__(self): 
+        self.head = None
+
+    # Function to insert a new 
+    # node at the beginning 
+    def push(self, new_data): 
+        new_node = Node(new_data) 
+        new_node.next = self.head 
+        self.head = new_node 
+
+    # Utility function to print it 
+    # the linked LinkedList 
+    def printList(self): 
+        temp = self.head 
+        while(temp): 
+            print (temp.data, end =" ") 
+            temp = temp.next
+
+
+    def detectLoop(self): 
+         s = set() 
+         temp = self.head 
+         while (temp): 
+
+             # If we have already has 
+             # this node in hashmap it 
+             # means their is a cycle 
+             # (Because you we encountering 
+             # the node second time). 
+            if (temp in s): 
+                return True
+
+            # If we are seeing the node for 
+            # the first time, insert it in hash 
+            s.add(temp) 
+
+            temp = temp.next
+
+
+         return False
+
+# Driver program for testing 
+llist = LinkedList() 
+llist.push(20) 
+llist.push(4) 
+llist.push(15) 
+llist.push(10) 
+
+# Create a loop for testing 
+llist.head.next.next.next.next = llist.head; 
+
+if( llist.detectLoop()): 
+    print ("Loop found") 
+else : 
+    print ("No Loop ") 
+
+