Longest Arithmetic Subsequence

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Problem Statement

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

Note that:

A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.

A sequence seq is arithmetic if seq[i + 1] - seq[i] are all the same value (for 0 <= i < seq.length - 1 ).

Examples

Example 1

Input: nums = [3,6,9,12]
Output: 4
The whole array is an arithmetic sequence with steps of length = 3.

Example 2

Input: nums = [9,4,7,2,10]
Output: 3
The longest arithmetic subsequence is [4,7,10].

Example 3

Input: nums = [20,1,15,3,10,5,8]
Output: 4
The longest arithmetic subsequence is [20,15,10,5].

Constraints

2 <= nums.length <= 1000

0 <= nums[i] <= 500

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicHash Table