HP Coding Interview Questions
25 HP coding interview problems with full optimal solutions — 8 easy, 12 medium, 5 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an HP interviewer values, and a FAQ section.
Showing 8 problems of 25
- #1easyvery frequently asked
1. Two Sum
HP's firmware and driver teams frequently use look-up tables for O(1) dispatch — Two Sum tests whether you instinctively reach for a hash map instead of a brute-force scan, which matters when your code runs on embedded microcontrollers with tight loop budgets.
- #9easyoccasionally asked
9. Palindrome Number
HP firmware and driver code handles numeric identifiers for device serial numbers, cartridge IDs, and page counters. Palindrome Number tests digit-manipulation skills without string conversion — a meaningful constraint in embedded C where string allocation is expensive.
- #20easyfrequently asked
20. Valid Parentheses
Parsing structured expressions is core to HP's firmware configuration parsers and printer command languages (PCL/PJL). Valid Parentheses tests whether you can maintain state with a stack — the same discipline behind device-command validation.
- #21easyfrequently asked
21. Merge Two Sorted Lists
HP's device-driver and print-spooler stacks frequently merge ordered queues of pending jobs from multiple input sources. Merging two sorted linked lists is the fundamental building block — HP uses it to verify that candidates handle pointer manipulation without losing data.
- #53easyfrequently asked
53. Maximum Subarray
HP uses signal-processing algorithms in imaging and scanning products where finding the strongest contiguous signal window is a real computational task. Maximum Subarray (Kadane's algorithm) is the archetype: HP interviewers use it to test whether you can identify the single-pass greedy insight in a DP-flavored problem.
- #70easyfrequently asked
70. Climbing Stairs
Dynamic programming is central to HP's ink/toner optimization algorithms and cost-scheduling tools for enterprise print fleets. Climbing Stairs is the textbook DP entry point — HP uses it to confirm that candidates understand memoization and state transition before discussing more complex optimization problems.
- #121easyfrequently asked
121. Best Time to Buy and Sell Stock
HP's financial and enterprise analytics teams process time-series data from equipment telemetry and cost-optimization pipelines. This problem tests single-pass reasoning over sequential data — the same pattern used when scanning sensor readings for peak-to-trough performance differences.
- #206easyfrequently asked
206. Reverse Linked List
HP's systems software and firmware teams deal with linked structures constantly — job queues, device-descriptor chains, and print-spooler task lists. Reversing a linked list in-place is a fundamental pointer-manipulation exercise that HP uses to probe candidate comfort with low-level memory operations.