1027. Longest Arithmetic Subsequence
Array
Hash Table
Binary Search
Dynamic Programming
Given an array nums of integers, return the length of the longest arithmetic subsequence in nums.
Note that:
Examples
Example 1
Input: nums = [3,6,9,12]
Output: 4
Explanation: The whole array is an arithmetic sequence with steps of length = 3.
Example 2
Input: nums = [9,4,7,2,10]
Output: 3
Explanation: The longest arithmetic subsequence is [4,7,10].
Example 3
Input: nums = [20,1,15,3,10,5,8]
Output: 4
Explanation: The longest arithmetic subsequence is [20,15,10,5].
Constraints
2 <= nums.length <= 10000 <= nums[i] <= 500