Clone Linked List with Random Pointer in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a 'random pointer' in a linked list?

A random pointer is an extra pointer in each node of a linked list that can point to any node in the list or be null. It is different from the usual 'next' pointer which points to the next node.

intermediate

Why do we need to clone a linked list with random pointers carefully?

Because each node has two pointers (next and random), simply copying nodes and next pointers is not enough. We must also correctly copy the random pointers to point to the corresponding cloned nodes.

intermediate

What is the first step in the common approach to clone a linked list with random pointers?

The first step is to create a new cloned node for each original node and insert it right after the original node in the list. This helps to keep track of the mapping between original and cloned nodes without extra space.

advanced

How do we set the random pointers of the cloned nodes in the interleaved list?

For each original node, its cloned node is right next to it. We set the cloned node's random pointer to the original node's random pointer's next node (which is the clone of the random node).

advanced

What is the final step after setting next and random pointers in the cloned linked list?

We separate the interleaved list into two lists: the original list and the cloned list, restoring the original list's next pointers and extracting the cloned list with correct next and random pointers.

What does the 'random' pointer in a linked list node point to?

A Any node in the list or null

B Only the next node

C The previous node

D The head node

The random pointer can point to any node in the list or be null.

In cloning a linked list with random pointers, what is the purpose of inserting cloned nodes between original nodes?

A To reverse the list

B To keep track of original-to-clone mapping without extra space

C To delete random pointers

D To sort the list

Inserting cloned nodes between original nodes helps map original nodes to their clones without using extra memory.

How do you assign the random pointer of a cloned node?

A Clone's random = original's random's next

B Clone's random = original's next

C Clone's random = original's random

D Clone's random = null

Because cloned nodes are inserted after original nodes, original's random's next is the clone of the random node.

What is the time complexity of cloning a linked list with random pointers using the interleaving method?

A O(n^2)

B O(log n)

C O(n)

D O(1)

The interleaving method clones the list in linear time, O(n), where n is the number of nodes.

After cloning, how do you restore the original linked list?

A By reversing the list

B By deleting cloned nodes

C By setting all random pointers to null

D By skipping cloned nodes and linking original nodes' next pointers

We restore the original list by linking original nodes' next pointers, skipping the cloned nodes.

Explain the step-by-step process to clone a linked list with random pointers without using extra space.

Think about how to keep track of original and cloned nodes together.

Why can't we just copy the nodes and their next pointers to clone a linked list with random pointers?

Consider what happens to random pointers in a simple copy.