Create LOOP DETECTION.py

LOOP DETECTION.py

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+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 already have
+            # this node in hashmap it
+            # means there is a cycle
+            # (Because we are 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 ")