Add clone list with random pointers

rp-code9 · rp-code9 · commit f482663ca0fd · 2021-04-06T23:24:14.000+05:30
diff --git a/README.md b/README.md
@@ -88,6 +88,7 @@ Princeton Algorithms [Part 1](https://www.coursera.org/learn/algorithms-part1/)
 * Sort linked list
     * Simple method [C++](problems/linked-list/SortLinkedListMethod1.cpp)
     * Using merge sort [C++](problems/linked-list/SortLinkedListMethod2.cpp)
+* Clone list with random pointers [C++](problems/linked-list/CloneListWithRandomPointer.cpp)
 
 ## Stack
 * Dynamic Stack [Java](problems/stack/DynamicStack.java)
diff --git a/problems/linked-list/CloneListWithRandomPointer.cpp b/problems/linked-list/CloneListWithRandomPointer.cpp
@@ -0,0 +1,140 @@
+// Techie Delight https://www.techiedelight.com/clone-a-linked-list-with-random-pointers/
+// Leetcode https://leetcode.com/explore/interview/card/top-interview-questions-hard/117/linked-list/841/
+
+#include <iostream>
+#include <vector>
+#include <unordered_map>
+
+class LinkedList
+{
+private:
+    class Node
+    {
+    public:
+        int key;
+        Node* next;
+        Node* random;
+
+        Node(int k) : key(k), next(nullptr) { }
+        Node() : key(0), next(nullptr) { }
+    };
+
+    Node* head;
+
+    void populateRandom()
+    {
+        if (head == nullptr) {
+            return;
+        }
+
+        Node* current = head;
+        while (current != nullptr) {
+            if (current->next != nullptr) {
+                current->random = current->next->next;
+            }
+
+            current = current->next;
+        }
+    }
+
+public:
+    LinkedList() : head(nullptr) { }
+
+    ~LinkedList()
+    {
+        Node* current = head;
+        while (current != nullptr) {
+            Node* temp = current;
+            current = current->next;
+            delete temp;
+        }
+        head = nullptr;
+    }
+
+    void push(int key)
+    {
+        Node* node = new Node(key);
+        if (head != nullptr) {
+            node->next = head;
+        }
+        head = node;
+    }
+
+    void createList(std::vector<int>& keys)
+    {
+        for (auto key : keys) {
+            push(key);
+        }
+        populateRandom();
+    }
+
+    void print()
+    {
+        if (head == nullptr) {
+            std::cout << "null\n";
+            return;
+        }
+
+        Node* current = head;
+        while (current != nullptr) {
+            if (current->random != nullptr) {
+                std::cout << current->key << "(" << current->random->key << ") ";
+            } else {
+                std::cout << current->key << "(null) ";
+            }
+            current = current->next;
+            if (current != nullptr) {
+                std::cout << "-> ";
+            }
+        }
+        std::cout << "\n";
+    }
+
+    Node* cloneList(Node* head, std::unordered_map<Node*, Node*>& map)
+    {
+        if (head == nullptr) {
+            return nullptr;
+        }
+
+        map[head] = new Node(head->key);
+        map[head]->next = cloneList(head->next, map);
+
+        return map[head];
+    }
+
+    void updateRandomPointer(Node* head, std::unordered_map<Node*, Node*>& map)
+    {
+        if (map[head] == nullptr) {
+            return;
+        }
+        map[head]->random = map[head->random];
+        updateRandomPointer(head->next, map);
+    }
+
+    LinkedList clone()
+    {
+        LinkedList list;
+        if (head == nullptr) {
+            return list;
+        }
+
+        std::unordered_map<Node*, Node*> map;
+        list.head = cloneList(head, map);
+        updateRandomPointer(head, map);
+
+        return list;
+    }
+};
+
+int main()
+{
+    std::vector<int> keys {6, 3, 4, 8, 2, 9, 10, 5, 1};
+    LinkedList list;
+    list.createList(keys);
+    list.print();
+    std::cout << "Cloned list : \n";
+    LinkedList cList = list.clone();
+    cList.print();
+
+    return 0;
+}
diff --git a/problems/linked-list/SortLinkedListMethod2.cpp b/problems/linked-list/SortLinkedListMethod2.cpp
@@ -120,8 +120,6 @@ class LinkedList
         std::cout << "\n";
     }
 
-
-
     void mergesort()
     {
         mergesort(&head);

Original file line number	Diff line number	Diff line change
`@@ -120,8 +120,6 @@ class LinkedList`
`120`	`120`	`std::cout << "\n";`
`121`	`121`	`}`
`122`	`122`
`123`		`-`
`124`		`-`
`125`	`123`	`void mergesort()`
`126`	`124`	`{`
`127`	`125`	`mergesort(&head);`