Merge pull request keshavsingh4522#876 from KhushiChaudhary744/master

 Detection of linkedlist in java keshavsingh4522#874

Java/detect_and_create_loop.jav

@@ -0,0 +1,107 @@
+import java.util.*;
+import java.util.Scanner;
+public class LinkedList {
+
+ static Node head; // head of list
+
+ static class Node // Linked list Node
+ {
+ int data; //to store value
+ Node next; //pointer
+ Node(int d) {
+ data = d;
+ next = null;
+ }
+ }
+
+ static int countNodes(Node ptr) //Function to count the number of nodes present
+ {
+ int count = 0;
+ while (ptr != null) {
+ ptr = ptr.next;
+ count++;
+ }
+ return count;
+ }
+
+ static public void push(int new_data) // Function to inserts a new Node at front of the list 
+ {
+
+ Node new_node = new Node(new_data); //Allocate a pointer/node and store the data
+
+ new_node.next = head; // make next of new Node as head 
+
+ head = new_node; // Move the head to point to new Node.
+ }
+
+ static void printList(Node head, int total_nodes) //function to traverse through the list and print all data values
+ {
+ Node curr = head;
+ int count = 0;
+ while (count < total_nodes) {
+ count++;
+ System.out.print(curr.data + " ");
+ curr = curr.next;
+ }
+ }
+
+ static Node makeloop(Node head_ref, int k) {
+ Node temp = head_ref;
+ int count = 1;
+ while (count < k) //traverrse the list till point is found
+ {
+ temp = temp.next;
+ count++;
+ }
+
+ Node connected_point = temp;
+
+ while (temp.next != null) // traverse remaining nodes
+ temp = temp.next;
+
+ temp.next = connected_point; //connect last node to k-th element
+ return head_ref;
+ }
+
+ static boolean detectLoop(Node h) //Function to detect loop, retuens true if loop is in linked list else returns false.
+ {
+ HashSet < Node > traverse = new HashSet < Node > ();
+ while (n != null) {
+
+ if (traverse.contains(n)) //if the hash a;ready contains a record of the node encountered true is returned as a loop isdetected
+ return true;
+
+ traverse.add(n);
+ n = n.next;
+ }
+ return false;
+ }
+
+ public static void main(String[] args) {
+ LinkedList l = new LinkedList();
+
+ Scanner sc = new Scanner(System.in);
+
+ print("Enter elements in the list, to stop entering press any alphabetical key");
+ while (true) {
+ try {
+ i = sc.nextInt();
+ l.push(i);
+ } catch (Exception e) {
+ System.out.println("Creating loop for run");
+ }
+ }
+ System.out.println("Enter the location to generate loop");
+ int k = sc.nextInt()
+ System.out.print("Given list");
+ printList(head, total_nodes);
+ head = makeloop(head, k);
+ System.out.print("Modified list with loop");
+ printList(head, total_nodes);
+
+ if (detectLoop(head))
+ System.out.println("Loop found");
+ else
+ System.out.println("No Loop");
+ }
+}