1218. Longest Arithmetic Subsequence of Given Difference
https://leetcode.com/problems/longest-arithmetic-subsequence-of-given-difference
Description
Given an integer array arr
and an integer difference
, return the length of the longest subsequence in arr
which is an arithmetic sequence such that the difference between adjacent elements in the subsequence equals difference
.
A subsequence is a sequence that can be derived from arr
by deleting some or no elements without changing the order of the remaining elements.
Example 1:
**Input:** arr = [1,2,3,4], difference = 1
**Output:** 4
**Explanation:** The longest arithmetic subsequence is [1,2,3,4].
Example 2:
**Input:** arr = [1,3,5,7], difference = 1
**Output:** 1
**Explanation:** The longest arithmetic subsequence is any single element.
Example 3:
**Input:** arr = [1,5,7,8,5,3,4,2,1], difference = -2
**Output:** 4
**Explanation:** The longest arithmetic subsequence is [7,5,3,1].
Constraints:
1 <= arr.length <= 105
-104 <= arr[i], difference <= 104
ac
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