add solution for 138.Copy List With Random Pointer in Kotlin

Author: t3chkid

kotlin/138-Copy-List-With-Random-Pointer.kt

@@ -0,0 +1,35 @@
+package kotlin
+
+class Node(var `val`: Int) {
+    var next: Node? = null
+    var random: Node? = null
+}
+
+class Solution {
+    fun copyRandomList(node: Node?): Node? {
+        if (node == null) return null
+        val hashMap = HashMap<Node, Node>()
+        val dummyNode = Node(-1)
+        var currentNode = node
+        var currentResultantListNode: Node? = dummyNode
+        // create the new linked list ignoring the random pointers
+        while (currentNode != null) {
+            val newNode = Node(currentNode.`val`)
+            currentResultantListNode?.next = newNode
+            // associate the node of the original list to the related new node
+            hashMap[currentNode] = newNode
+            currentResultantListNode = newNode
+            currentNode = currentNode.next
+        }
+        currentNode = node
+        currentResultantListNode = dummyNode.next
+        // make the "random" pointers of each node in the new list,
+        // match those of the original list
+        while (currentNode != null) {
+            if (currentNode.random != null) currentResultantListNode?.random = hashMap[currentNode!!.random]
+            currentNode = currentNode.next
+            currentResultantListNode = currentResultantListNode?.next
+        }
+        return dummyNode.next
+    }
+}