{ "data": { "question": { "questionId": "1087", "questionFrontendId": "1027", "boundTopicId": null, "title": "Longest Arithmetic Subsequence", "titleSlug": "longest-arithmetic-subsequence", "content": "

Given an array nums of integers, return the length of the longest arithmetic subsequence in nums.

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Recall that a subsequence of an array nums is a list nums[i1], nums[i2], ..., nums[ik] with 0 <= i1 < i2 < ... < ik <= nums.length - 1, and that a sequence seq is arithmetic if seq[i+1] - seq[i] are all the same value (for 0 <= i < seq.length - 1).

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Example 1:

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\nInput: nums = [3,6,9,12]\nOutput: 4\nExplanation: \nThe whole array is an arithmetic sequence with steps of length = 3.\n
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Example 2:

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\nInput: nums = [9,4,7,2,10]\nOutput: 3\nExplanation: \nThe longest arithmetic subsequence is [4,7,10].\n
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Example 3:

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\nInput: nums = [20,1,15,3,10,5,8]\nOutput: 4\nExplanation: \nThe longest arithmetic subsequence is [20,15,10,5].\n
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Constraints:

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