From b8e22ebe39acb6d5b0c482cd052036a1ac7e1fc2 Mon Sep 17 00:00:00 2001
From: Jawakar Sri <118127168+jawakarsri@users.noreply.github.com>
Date: Tue, 1 Oct 2024 10:39:14 +0530
Subject: [PATCH] Create Copy List with Random Pointer

---
 .../Linked List/Copy List with Random Pointer | 94 +++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Java/Linked List/Copy List with Random Pointer

diff --git a/Java/Linked List/Copy List with Random Pointer b/Java/Linked List/Copy List with Random Pointer
new file mode 100644
index 00000000..c06e5778
--- /dev/null
+++ b/Java/Linked List/Copy List with Random Pointer	
@@ -0,0 +1,94 @@
+// Author: Jawakar Sri
+// Date Created: 01/10/2024
+// Title: LeetCode Problem - Copy List with Random Pointer
+// Problem Link: https://leetcode.com/problems/copy-list-with-random-pointer/
+
+// Definition for a Node.
+class Node {
+    int val;
+    Node next;
+    Node random;
+    public Node(int val) {
+        this.val = val;
+        this.next = null;
+        this.random = null;
+    }
+}
+
+// Solution 1: Using extra space (HashMap)
+class SolutionUsingHashMap {
+    public Node copyRandomList(Node head) {
+        if (head == null) return null;
+
+        Node curr = head, newHead = new Node(0);
+        Node newCurr = newHead;
+        HashMap<Node, Node> map = new HashMap();
+
+        // First pass: Create new nodes and store them in the map
+        while (curr != null) {
+            if (!map.containsKey(curr)) {
+                newCurr.next = new Node(curr.val);
+                map.put(curr, newCurr.next);
+            } else {
+                newCurr.next = map.get(curr);
+            }
+
+            newCurr = newCurr.next;
+
+            // Create random pointers
+            if (curr.random != null) {
+                if (!map.containsKey(curr.random)) {
+                    newCurr.random = new Node(curr.random.val);
+                    map.put(curr.random, newCurr.random);
+                } else {
+                    newCurr.random = map.get(curr.random);
+                }
+            }
+
+            curr = curr.next;
+        }
+
+        return newHead.next;
+    }
+}
+
+// Solution 2: Constant space (In-place modification)
+class SolutionUsingInPlace {
+    public Node copyRandomList(Node head) {
+        if (head == null) return null;
+
+        Node curr = head;
+
+        // Step 1: Create a new node for each original node and link them in place
+        while (curr != null) {
+            Node next = curr.next;
+            curr.next = new Node(curr.val);
+            curr.next.next = next;
+            curr = next;
+        }
+
+        // Step 2: Set random pointers for the copied nodes
+        curr = head;
+        while (curr != null) {
+            if (curr.random != null) {
+                curr.next.random = curr.random.next;
+            }
+            curr = curr.next.next;
+        }
+
+        // Step 3: Separate the original and copied lists
+        curr = head;
+        Node newHead = new Node(0); // Dummy node
+        Node newCurr = newHead;
+
+        while (curr != null) {
+            Node next = curr.next.next;
+            newCurr.next = curr.next;
+            newCurr = newCurr.next;
+            curr.next = next;
+            curr = next;
+        }
+
+        return newHead.next;
+    }
+}