Copy list with random pointers

Author: TonyStark-19

Linked-list/CopyListWithRandomPointers.cpp

@@ -0,0 +1,155 @@
+#include <iostream>
+#include <unordered_map>
+using namespace std;
+
+// Node class to create a node
+class Node
+{
+public:
+    int data;
+    Node *next;
+    Node *random;
+
+    Node(int val)
+    {
+        data = val;
+        next = NULL;
+        random = NULL;
+    }
+};
+
+// List class to manage linked list operations
+class List
+{
+public:
+    Node *head;
+    Node *tail;
+
+    List()
+    {
+        head = tail = NULL;
+    }
+
+    void push_back(int val) // Add node to the end
+    {
+        Node *newNode = new Node(val);
+
+        if (head == NULL) // Empty linked list
+        {
+            head = tail = newNode;
+        }
+        else
+        {
+            tail->next = newNode;
+            tail = newNode;
+        }
+    }
+
+    void setRandom(int nodeIndex, int randomIndex) // to set random pointers
+    {
+        if (!head)
+            return;
+
+        Node *temp = head;
+        Node *randomNode = head;
+        int count = 0;
+
+        while (temp && count < nodeIndex)
+        {
+            temp = temp->next;
+            count++;
+        }
+
+        count = 0;
+        while (randomNode && count < randomIndex)
+        {
+            randomNode = randomNode->next;
+            count++;
+        }
+
+        if (temp)
+            temp->random = randomNode;
+    }
+
+    Node *copyRandomList(Node *head)
+    {
+        if (head == NULL) // base case
+        {
+            return NULL;
+        }
+
+        unordered_map<Node *, Node *> m;
+
+        Node *newHead = new Node(head->data);
+        Node *oldTemp = head->next;
+        Node *newTemp = newHead;
+        m[head] = newHead;
+
+        while (oldTemp != NULL) // plain copy
+        {
+            Node *copyNode = new Node(oldTemp->data);
+            m[oldTemp] = copyNode;
+            newTemp->next = copyNode;
+
+            oldTemp = oldTemp->next;
+            newTemp = newTemp->next;
+        }
+
+        oldTemp = head;
+        newTemp = newHead;
+
+        while (oldTemp != NULL) // random connections copy
+        {
+            newTemp->random = m[oldTemp->random];
+            oldTemp = oldTemp->next;
+            newTemp = newTemp->next;
+        }
+
+        return newHead;
+    }
+
+    void printLL(Node *head)
+    {
+        Node *temp = head;
+        while (temp != NULL)
+        {
+            cout << temp->data << " (random: ";
+            if (temp->random)
+                cout << temp->random->data;
+            else
+                cout << "NULL";
+            cout << ") -> ";
+            temp = temp->next;
+        }
+        cout << "NULL" << endl;
+    }
+};
+
+int main()
+{
+    List ll1;
+    ll1.push_back(1);
+    ll1.push_back(2);
+    ll1.push_back(3);
+    ll1.push_back(4);
+    ll1.push_back(5);
+
+    // Setting up random pointers
+    ll1.setRandom(0, 2); // Node 1 -> Node 3
+    ll1.setRandom(1, 4); // Node 2 -> Node 5
+    ll1.setRandom(2, 1); // Node 3 -> Node 2
+    ll1.setRandom(3, 3); // Node 4 -> Node 4
+    ll1.setRandom(4, 0); // Node 5 -> Node 1
+
+    cout << "Original List:" << endl;
+    ll1.printLL(ll1.head);
+
+    // Copying the linked list
+    List ll2;
+    ll2.head = ll1.copyRandomList(ll1.head);
+
+    cout << "Copied List:" << endl;
+    ll2.printLL(ll2.head);
+
+    return 0;
+}