Remove Nth Node from End of List in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main idea behind removing the Nth node from the end of a linked list?

Use two pointers spaced N nodes apart. Move both until the second pointer reaches the end. The first pointer will then be just before the node to remove.

beginner

Why do we use a dummy node at the start of the linked list in this problem?

A dummy node helps handle edge cases, like removing the first node, by providing a fixed node before the head.

intermediate

In the two-pointer approach, what happens if the fast pointer moves N steps and reaches NULL immediately?

It means we need to remove the head node because the list length equals N.

beginner

What is the time complexity of removing the Nth node from the end of a singly linked list using the two-pointer method?

O(L), where L is the length of the list, because we traverse the list at most twice.

intermediate

How do you update the pointers to remove the target node once the first pointer is just before it?

Set first->next = first->next->next to skip the target node and free its memory if needed.

What does the fast pointer do initially in the two-pointer approach?

A Moves N steps ahead

B Moves one step

C Stays at the head

D Moves to the end immediately

The fast pointer moves N steps ahead to create a gap of N nodes between fast and slow pointers.

Why is a dummy node useful when removing the Nth node from the end?

A It stores the value of the removed node

B It prevents memory leaks

C It helps handle removal of the head node easily

D It speeds up the traversal

A dummy node simplifies edge cases like removing the head by providing a stable node before the head.

If the list has 5 nodes and N=5, which node is removed?

A First node

B Last node

C Third node

D Second node

Removing the 5th node from the end means removing the first node in a 5-node list.

What is the space complexity of the two-pointer method for this problem?

A O(N^2)

B O(N)

C O(log N)

D O(1)

The method uses only a few pointers, so space complexity is constant O(1).

After positioning the pointers, how do you remove the target node?

A Set target->next = NULL

B Set previous->next = target->next

C Delete the entire list

D Swap values with next node

You skip the target node by linking the previous node directly to the node after the target.

Explain step-by-step how to remove the Nth node from the end of a singly linked list using two pointers.

Think about how spacing the pointers helps find the node to remove.

Describe how edge cases like removing the head node are handled in the Remove Nth Node from End of List problem.

Consider what happens when N equals the list length.