In this post, we are going to solve the Copy List with Random Pointer Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

Problem
A linked list of length n
is given such that each node contains an additional random pointer, which could point to any node in the list, or null
.
Construct a deep copy of the list. The deep copy should consist of exactly n
brand new nodes, where each new node has its value set to the value of its corresponding original node. Both the next
and random
pointer of the new nodes should point to new nodes in the copied list such that the pointers in the original list and copied list represent the same list state. None of the pointers in the new list should point to nodes in the original list.
For example, if there are two nodes X
and Y
in the original list, where X.random --> Y
, then for the corresponding two nodes x
and y
in the copied list, x.random --> y
.
Return the head of the copied linked list.
The linked list is represented in the input/output as a list of n
nodes. Each node is represented as a pair of [val, random_index]
where:
val
: an integer representingNode.val
random_index
: the index of the node (range from0
ton-1
) that therandom
pointer points to, ornull
if it does not point to any node.
Your code will only be given the head
of the original linked list.
Example 1:

Input: head = [[7,null],[13,0],[11,4],[10,2],[1,0]] Output: [[7,null],[13,0],[11,4],[10,2],[1,0]]
Example 2:

Input: head = [[1,1],[2,1]] Output: [[1,1],[2,1]]
Example 3:

Input: head = [[3,null],[3,0],[3,null]] Output: [[3,null],[3,0],[3,null]]
Constraints:
0 <= n <= 1000
-104 <= Node.val <= 104
Node.random
isnull
or is pointing to some node in the linked list.
Now, let’s see the leetcode solution of Copy List with Random Pointer Leetcode Solution.
Copy List with Random Pointer Leetcode Solution in Python
class Solution: def copyRandomList(self, head: 'Node') -> 'Node': if not head: return None if head in self.map: return self.map[head] newNode = Node(head.val) self.map[head] = newNode newNode.next = self.copyRandomList(head.next) newNode.random = self.copyRandomList(head.random) return newNode map = {}
Copy List with Random Pointer Leetcode Solution in CPP
class Solution { public: Node* copyRandomList(Node* head) { if (head == nullptr) return nullptr; if (map.count(head)) return map[head]; Node* newNode = new Node(head->val); map[head] = newNode; newNode->next = copyRandomList(head->next); newNode->random = copyRandomList(head->random); return newNode; } private: unordered_map<Node*, Node*> map; };
Copy List with Random Pointer Leetcode Solution in Java
class Solution { public Node copyRandomList(Node head) { if (head == null) return null; if (map.containsKey(head)) return map.get(head); Node newNode = new Node(head.val); map.put(head, newNode); newNode.next = copyRandomList(head.next); newNode.random = copyRandomList(head.random); return newNode; } private Map<Node, Node> map = new HashMap<>(); }
Note: This problem Copy List with Random Pointer is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purpose.