1027.longest-arithmetic-subsequence.py

from lc import *

class Solution:
    def longestArithSeqLength(self, a: List[int]) -> int:
        d = {}
        for i in range(len(a)):
            for j in range(i+1, len(a)):
                d[j,a[j]-a[i]]=d.get((i,a[j]-a[i]),1)+1
        return max(d.values())

class Solution:
    def longestArithSeqLength(self, a: List[int]) -> int:
        d={};n=len(a);[setitem(d,(j,a[j]-a[i]),d.get((i,a[j]-a[i]),1)+1)for i in range(n)for j in range(i+1,n)];return max(d.values())

class Solution:
    def longestArithSeqLength(self, a: List[int]) -> int:
        d={};r=range;[setitem(d,(i,t:=a[j]-a[i]),d.get((j,t),1)+1)for i in r(len(a))for j in r(i)];return max(d.values())

test('''
1027. Longest Arithmetic Subsequence
Medium

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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).
 

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 <= 1000
0 <= nums[i] <= 500
''')