Clone linked list with random pointer (#180)

linked-lists/README.md

@@ -4,22 +4,24 @@
 
 1. [Singly Linked List](c-or-cpp/singly.cpp)
 2. [Reversing Linked List](c-or-cpp/reverse.cpp)
-2. [Doubly Linked List](c-or-cpp/doubly.cpp)
-3. [Circular Linked List](c-or-cpp/circular.cpp)
-4. [Insertion Linked List](c-or-cpp/all-possible-insertion.cpp)
-5. [Josephus Problem Using Circular Linked List](c-or-cpp/josephus-problem.c)
+3. [Doubly Linked List](c-or-cpp/doubly.cpp)
+4. [Circular Linked List](c-or-cpp/circular.cpp)
+5. [Insertion Linked List](c-or-cpp/all-possible-insertion.cpp)
+6. [Josephus Problem Using Circular Linked List](c-or-cpp/josephus-problem.c)
 
 ### Java
 
 1. [Singly Linked List](java/singly.java)
 2. [Doubly Linked List](java/doubly.java)
-2. [Circular Linked List](java/circular.java)
-2. [Reverse Linked List](java/reverse.java)
+3. [Circular Linked List](java/circular.java)
+4. [Reverse Linked List](java/reverse.java)
+5. [Clone Linked List with Random Pointer](java/clone-linkedlist-with-rnd-pointer.java)
 
 ### JavaScript
 
 1. [Singly Linked List](js/singly.js)
 
 ### Python
+
 1. [Singly Linked List](Python/singly.py)
 2. [Doubly Linked List](Python/doubly.py)

linked-lists/java/clone-linkedlist-with-rnd-pointer.java

@@ -0,0 +1,125 @@
+// Java program to clone a linked list with random pointers
+import java.util.HashMap;
+import java.util.Map;
+  
+// Linked List Node class
+class Node
+{
+    int data;//Node data
+    Node next, random;//Next and random reference
+  
+    //Node constructor
+    public Node(int data)
+    {
+        this.data = data;
+        this.next = this.random = null;
+    }
+}
+  
+// linked list class
+class LinkedList
+{
+    Node head;//Linked list head reference
+  
+    // Linked list constructor
+    public LinkedList(Node head)
+    {
+        this.head = head;
+    }
+  
+    // push method to put data always at the head
+    // in the linked list.
+    public void push(int data)
+    {
+        Node node = new Node(data);
+        node.next = this.head;
+        this.head = node;
+    }
+  
+    // Method to print the list.
+    void print()
+    {
+        Node temp = head;
+        while (temp != null)
+        {
+            Node random = temp.random;
+            int randomData = (random != null)? random.data: -1;
+            System.out.println("Data = " + temp.data +
+                               ", Random data = "+ randomData);
+            temp = temp.next;
+        }
+    }
+  
+    // Actual clone method which returns head
+    // reference of cloned linked list.
+    public LinkedList clone()
+    {
+        // Initialize two references, one with original
+        // list's head.
+        Node origCurr = this.head, cloneCurr = null;
+  
+        // Hash map which contains node to node mapping of
+        // original and clone linked list.
+        Map<Node, Node> map = new HashMap<Node, Node>();
+  
+        // Traverse the original list and make a copy of that
+        // in the clone linked list.
+        while (origCurr != null)
+        {
+            cloneCurr = new Node(origCurr.data);
+            map.put(origCurr, cloneCurr);
+            origCurr = origCurr.next;
+        }
+  
+        // Adjusting the original list reference again.
+        origCurr = this.head;
+  
+        // Traversal of original list again to adjust the next
+        // and random references of clone list using hash map.
+        while (origCurr != null)
+        {
+            cloneCurr = map.get(origCurr);
+            cloneCurr.next = map.get(origCurr.next);
+            cloneCurr.random = map.get(origCurr.random);
+            origCurr = origCurr.next;
+        }
+  
+        //return the head reference of the clone list.
+        return new LinkedList(map.get(this.head));
+    }
+}
+  
+// Driver Class
+class Main
+{
+    // Main method.
+    public static void main(String[] args)
+    {
+        // Pushing data in the linked list.
+        LinkedList list = new LinkedList(new Node(5));
+        list.push(4);
+        list.push(3);
+        list.push(2);
+        list.push(1);
+  
+        // Setting up random references.
+        list.head.random = list.head.next.next;
+        list.head.next.random =
+            list.head.next.next.next;
+        list.head.next.next.random =
+            list.head.next.next.next.next;
+        list.head.next.next.next.random =
+            list.head.next.next.next.next.next;
+        list.head.next.next.next.next.random =
+            list.head.next;
+  
+        // Making a clone of the original linked list.
+        LinkedList clone = list.clone();
+  
+        // Print the original and cloned linked list.
+        System.out.println("Original linked list");
+        list.print();
+        System.out.println("\nCloned linked list");
+        clone.print();
+    }
+}