Length of Loop in Linked List

src/ds_002_linkedlists/LengthOfLoopInLinkedList.java

@@ -0,0 +1,77 @@
+// Java program to count number of nodes 
+// in loop in a linked list if loop is 
+// present 
+import java.io.*; 
+
+class GFG { 
+
+
+/* Link list node */
+static class Node 
+{ 
+	int data; 
+	Node next; 
+	Node(int data) 
+	{ 
+		this.data =data; 
+		next =null; 
+	} 
+} 
+
+// Returns count of nodes present in loop. 
+static int countNodes( Node n) 
+{ 
+int res = 1; 
+Node temp = n; 
+while (temp.next != n) 
+{ 
+	res++; 
+	temp = temp.next; 
+} 
+return res; 
+} 
+
+/* This function detects and counts loop 
+nodes in the list. If loop is not there 
+in then returns 0 */
+static int countNodesinLoop( Node list) 
+{ 
+	Node slow_p = list, fast_p = list; 
+
+	while (slow_p !=null && fast_p!=null && fast_p.next!=null) 
+	{ 
+		slow_p = slow_p.next; 
+		fast_p = fast_p.next.next; 
+
+		/* If slow_p and fast_p meet at some point 
+		then there is a loop */
+		if (slow_p == fast_p) 
+			return countNodes(slow_p); 
+	} 
+
+	/* Return 0 to indeciate that ther is no loop*/
+	return 0; 
+} 
+
+static Node newNode(int key) 
+{ 
+	Node temp = new Node(key); 
+
+	return temp; 
+} 
+
+/* Driver program to test above function*/
+	public static void main (String[] args) { 
+		Node head = newNode(1); 
+	head.next = newNode(2); 
+	head.next.next = newNode(3); 
+	head.next.next.next = newNode(4); 
+	head.next.next.next.next = newNode(5); 
+
+	/* Create a loop for testing */
+	head.next.next.next.next.next = head.next; 
+
+	System.out.println( countNodesinLoop(head)); 
+	} 
+} 
+// This code is contributed by inder_verma.