Linked Lists and Pointer Manipulation Questions

Comprehensive knowledge of linked list data structures and pointer based implementations. Covers singly linked lists, doubly linked lists, circular lists, and node based sequential structures. Candidates should be able to implement and reason about core operations including traversal, insertion, deletion, reversing a list, finding the middle element, removing the nth node from the end, detecting and removing cycles, merging sorted lists, partitioning lists, computing intersection nodes, and other in place transformations. Emphasize pointer and reference manipulation techniques, manual memory allocation and deallocation, ownership and lifetime considerations, and debugging strategies for pointer errors and memory leaks, particularly in manual memory management languages such as C and C plus plus. Also cover implementation techniques such as iterative and recursive approaches, use of dummy head or sentinel nodes to simplify edge cases, and in place algorithms to minimize extra memory. Discuss algorithmic complexity and trade offs relative to contiguous arrays, including dynamic resizing, memory locality, and cache behavior, and when linked lists are the appropriate abstraction such as in embedded systems or when implementing free lists and adjacency lists. Interviewers may probe both low level pointer manipulation and higher level reasoning about when to use list based structures and how list concepts extend into more complex data structures.

HardSystem Design

0 practiced

Design a thread-safe append-only queue where producers append to tail and consumers pop from head. Compare a simple mutex-based linked-list queue with a lock-free Michael-Scott queue: describe pointer manipulations, necessary memory reclamation, and expected throughput characteristics in a high-concurrency ingestion system.

MediumTechnical

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Describe how linked lists are used to represent adjacency lists for graphs in big-data processing. Explain memory layouts (per-vertex vector vs per-vertex linked list), trade-offs in random access and traversal, and techniques to make adjacency storage disk-friendly (CSR/CSR-like formats, compressed neighbor lists).

EasyTechnical

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Implement a singly linked list in C using the node definition `struct Node { int val; struct Node* next; };`. Write two functions: `void insert_head(struct Node** head, int value)` and `void insert_tail(struct Node** head, struct Node** tail, int value)`. Ensure `insert_tail` runs in O(1) time by maintaining a tail pointer, handle the empty list case, and include proper `malloc` checks and initialization for newly allocated nodes.

HardTechnical

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You are given k sorted singly linked lists where k may be large (tens of thousands or more). Describe and analyze efficient strategies to merge them into a single sorted linked list at data-engineering scale. Consider memory constraints, I/O if lists are disk-backed, and parallelism. Discuss multi-way merge, priority queues, and external merge-sort techniques.

MediumTechnical

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Implement in C a function `ListNode* merge_two_sorted_in_place(ListNode* a, ListNode* b)` where the two input lists may be very long and memory is constrained. The function must reuse nodes from inputs (no allocations). Also explain memory-access patterns and how to make the merge cache-friendly if inputs are stored in memory pools.

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