Last updated on January 7th, 2025 at 03:17 am
Here, we see the Copy List with Random Pointer LeetCode Solution. This Leetcode problem is solved using different approaches in many programming languages, such as C++, Java, JavaScript, Python, etc.
List of all LeetCode Solution
Topics
Hash Table, Linked List
Companies
Amazon, Bloomberg, Microsoft, Uber
Level of Question
Medium
Copy List with Random Pointer LeetCode Solution
Table of Contents
1. Problem Statement
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.valrandom_index: the index of the node (range from0ton-1) that therandompointer points to, ornullif 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]]
2. Coding Pattern Used in Solution
The coding pattern used in this code is “Hash Map for Node Cloning”. This is not one of the listed patterns, so we can consider it a new pattern. The approach involves using a hash map (or dictionary) to map original nodes to their corresponding cloned nodes, allowing us to efficiently copy a linked list with random pointers.
3. Code Implementation in Different Languages
3.1 Copy List with Random Pointer C++
class Solution {
public:
Node* copyRandomList(Node* head) {
if (!head) return nullptr;
unordered_map<Node*, Node*> old_to_new;
Node* curr = head;
while (curr) {
old_to_new[curr] = new Node(curr->val);
curr = curr->next;
}
curr = head;
while (curr) {
old_to_new[curr]->next = old_to_new[curr->next];
old_to_new[curr]->random = old_to_new[curr->random];
curr = curr->next;
}
return old_to_new[head];
}
};
3.2 Copy List with Random Pointer Java
public class Solution {
public Node copyRandomList(Node head) {
if (head == null) return null;
HashMap<Node, Node> oldToNew = new HashMap<>();
Node curr = head;
while (curr != null) {
oldToNew.put(curr, new Node(curr.val));
curr = curr.next;
}
curr = head;
while (curr != null) {
oldToNew.get(curr).next = oldToNew.get(curr.next);
oldToNew.get(curr).random = oldToNew.get(curr.random);
curr = curr.next;
}
return oldToNew.get(head);
}
}
3.3 Copy List with Random Pointer JavaScript
var copyRandomList = function(head) {
if (!head) return null;
const oldToNew = new Map();
let curr = head;
while (curr) {
oldToNew.set(curr, new Node(curr.val));
curr = curr.next;
}
curr = head;
while (curr) {
oldToNew.get(curr).next = oldToNew.get(curr.next) || null;
oldToNew.get(curr).random = oldToNew.get(curr.random) || null;
curr = curr.next;
}
return oldToNew.get(head);
};
3.4 Copy List with Random Pointer Python
class Solution(object):
def copyRandomList(self, head):
if not head:
return None
old_to_new = {}
curr = head
while curr:
old_to_new[curr] = Node(curr.val)
curr = curr.next
curr = head
while curr:
old_to_new[curr].next = old_to_new.get(curr.next)
old_to_new[curr].random = old_to_new.get(curr.random)
curr = curr.next
return old_to_new[head]
4. Time and Space Complexity
| Time Complexity | Space Complexity | |
| C++ | O(n) | O(n) |
| Java | O(n) | O(n) |
| JavaScript | O(n) | O(n) |
| Python | O(n) | O(n) |