CodingMediumcod-g941

Subject Dynamic programming 1dLevel Mid–Senior~25 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Given an integer array and an integer difference d, return the length of the longest subsequence (elements in original order, not necessarily contiguous) that forms an arithmetic sequence with common difference exactly d. The array has at most 100000 elements with values in [-10000, 10000].

Implement

longest_arith_subseq(arr: list[int], d: int) → int

Examples

in[[1,2,3,4],1]out4

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.