Reverse a singly linked list in place. Provide: 1) An iterative O(1)-extra-space solution and a recursive version; explain how you avoid stack overflow for up to 10^6 nodes (tail recursion elimination or chunked recursion). 2) Handling of edge cases: empty list, single node, very long list. 3) Behavior on cyclic lists: detect a cycle (Floyd’s) and either preserve the cycle orientation while reversing the linear segment or break the cycle—justify your choice and implement accordingly. 4) Time/space analysis, loop invariant for correctness, and minimal set of tests.

This question evaluates linked-list manipulation skills including in-place iterative reversal, recursive techniques, cycle detection and handling, time and space complexity analysis, loop invariants, and minimal test design.

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This is a hard difficulty Coding & Algorithms question, commonly asked during HR Screen rounds at NVIDIA.

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Reverse a singly linked list robustly | NVIDIA Interview Question

Reverse a Singly Linked List In-Place

Context: You are given the head of a standard singly linked list (each node has value and next). Implement and explain robust reversal routines that work for empty lists, single-node lists, very long lists (up to 10^6 nodes), and lists that may contain a cycle.

Requirements

Implement two versions:
- Iterative reversal with O(1) extra space.
- Recursive reversal. Explain how you avoid stack overflow for up to 10^6 nodes using either tail-recursion elimination (where available) or chunked recursion.
Edge cases:
- Empty list.
- Single node.
- Very long list (≈ 10^6 nodes).
Cycles:
- Detect a cycle using Floyd’s tortoise–hare algorithm.
- Choose one policy:
  - Preserve the cycle orientation while reversing the linear segment, or
  - Break the cycle before reversing.
- Justify your choice and implement accordingly.
Include:
- Time and space complexity analysis.
- A loop invariant to argue correctness of the iterative solution.
- A minimal but sufficient test set.

Requirements

Implement two versions:

Iterative reversal with O(1) extra space.
Recursive reversal. Explain how you avoid stack overflow for up to 10^6 nodes using either tail-recursion elimination (where available) or chunked recursion.

Edge cases:

Empty list.
Single node.
Very long list (≈ 10^6 nodes).

Cycles:

Detect a cycle using Floyd’s tortoise–hare algorithm.
Choose one policy:
- Preserve the cycle orientation while reversing the linear segment, or
- Break the cycle before reversing.
Justify your choice and implement accordingly.

Include:

Time and space complexity analysis.
A loop invariant to argue correctness of the iterative solution.
A minimal but sufficient test set.

Reverse a singly linked list robustly

Quick Overview

Reverse a Singly Linked List In-Place

Requirements

Solution

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Reverse a singly linked list robustly

Quick Overview

Reverse a Singly Linked List In-Place

Requirements

Solution

Comments (0)