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Advanced Data Structures and Implementation Questions

Deep and practical expertise in advanced data structures, their implementation details, performance characteristics, and selection for both algorithmic problems and production systems. Topics include arrays and dynamic arrays, strings, linked lists, stacks and queues, hash tables, heaps and priority queues, various tree forms including binary search trees and balanced trees, tries or prefix trees, segment trees and binary indexed trees or fenwick trees, union find or disjoint set union, suffix arrays, and advanced graph representations. Candidates should be able to implement core structures from first principles, demonstrate interfaces and invariants, reason about insertion deletion search traversal and iteration costs including worst case average case and amortized analysis, and discuss memory management and ownership in low level languages such as C and C plus plus as well as safe memory and reference use in managed languages. Evaluation also covers trade offs between contiguous and pointer based layouts, cache friendliness, concurrency considerations, selection of structures based on access patterns update frequency and memory constraints, handling of edge cases, testing and performance tuning for realistic inputs, and applying structures to problems such as top K queries prefix search connectivity range queries caches and union operations.

HardTechnical
92 practiced
Implement a persistent (immutable) segment tree in C++ that supports creating a new version after each point update and allows querying historical versions for range sum. Provide an API that returns a root pointer for each version and explain memory costs using path copying.
MediumTechnical
68 practiced
Implement a compressed adjacency representation for moderately dense graphs using bitsets (bit-packed adjacency matrix) to support fast neighbor iteration and boolean queries on edges. Provide functions to check edge existence and iterate neighbors efficiently, and discuss memory/time trade-offs compared to adjacency list and CSR.
HardTechnical
86 practiced
Implement a fixed-size memory pool allocator in C++ that provides O(1) allocation and deallocation for objects of the same size. Provide an interface allocate() and deallocate(ptr), describe free list management, alignment, and discuss how to make it thread-safe with low contention.
HardTechnical
76 practiced
Design a scalable concurrent priority queue with support for efficient increase-key and decrease-key in a multi-threaded environment. Discuss segmented heaps, concurrent skip lists, or combining-queue approaches to reduce contention. Explain how you'd test for correctness and measure throughput under mixed workloads.
MediumTechnical
74 practiced
Explain the suffix array data structure and describe the doubling algorithm to construct a suffix array in O(n log n) (or O(n log^2 n) depending on sorting). Provide the high-level steps and complexity analysis, and compare suffix arrays to suffix trees and suffix automata for substring queries.

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