Coding

Linked List

Asked at

Infosys

1Give yourself 5 minutes

2Answer out loud, not in your head

3Then compare with the answer below

Stuck? Show a way to structure it+

01Clarify whether the list is singly or doubly linked and whether nodes may be modified
02Draw the local before-and-after pointers
03Use dummy nodes when insertion or deletion may affect the head
04Save the next pointer before rewiring a node
05Validate empty, one-node, head, tail, and repeated-value cases

Reference answer

Start by clarifying the exact linked-list operation, because the stored title does not specify deletion, reversal, partitioning, or cycle detection. State the pointer invariant before mutation and draw a small example. For operations that can change the head, a dummy predecessor eliminates a special case. Before changing current.next, save the original next node so the remaining list is not lost; then reconnect one local relationship at a time. If the problem is delete-a-node-with-only-that-node, copy the next value and bypass it, while noting that it cannot delete the tail. If it is cycle detection, use slow and fast pointers and explain the meeting invariant. Test null input, one node, head and tail operations, duplicates, and invalid assumptions. Most single-pass pointer operations are O(n) time and O(1) extra space.

Then expect these follow-ups

What constraint would change your chosen approach?
Tests: constraint adaptation
How would you test the edge cases before implementation?
Tests: implementation extension

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