Create Copy_List_With_Random_Pointer.java

The Copy List with Random Pointer problem involves creating a deep copy of a linked list where each node has a next pointer and a random pointer (pointing to any other node or null). The solution uses a three-step approach: first, clone each node and place the clone next to the original; second, set the random pointers of each clone based on the original nodes' random pointers; finally, separate the original and cloned lists. This method efficiently creates the copied list with O(n) time complexity and O(1) auxiliary space.

Author: Tsurya06

src/main/java/com/thealgorithms/datastructures/lists/Copy_List_With_Random_Pointer.java

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+package com.thealgorithms.datastructures.lists;
+
+class Node {
+    int val;
+    Node next;
+    Node random;
+
+    public Node(int val) {
+        this.val = val;
+        this.next = null;
+        this.random = null;
+    }
+}
+
+public class Solution {
+    public Node copyRandomList(Node head) {
+        if (head == null) {
+            return null;
+        }
+
+        // Step 1: Clone each node and insert it next to the original node
+        Node current = head;
+        while (current != null) {
+            Node clone = new Node(current.val);
+            clone.next = current.next;
+            current.next = clone;
+            current = clone.next;
+        }
+
+        // Step 2: Set the random pointers for the cloned nodes
+        current = head;
+        while (current != null) {
+            if (current.random != null) {
+                current.next.random = current.random.next;
+            }
+            current = current.next.next;
+        }
+
+        // Step 3: Separate the original and cloned lists
+        Node original = head, copy = head.next;
+        Node clonedHead = head.next;
+        while (original != null) {
+            original.next = original.next.next;
+            if (copy.next != null) {
+                copy.next = copy.next.next;
+            }
+            original = original.next;
+            copy = copy.next;
+        }
+
+        return clonedHead;
+    }
+}
+