Algorithm

Problem Name: 1218. Longest Arithmetic Subsequence of Given Difference

Problem Link:   https://leetcode.com/problems/longest-arithmetic-subsequence-of-given-difference/
 

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

Code Examples

#1 Code Example with Python Programming

Code - Python Programming


class Solution:
    def longestSubsequence(self, arr: List[int], d: int) -> int:
        dp = collections.Counter()
        for a in arr:
            dp[a] = max(dp[a], dp[a - d] + 1)
        return max(dp.values())
Copy The Code & Try With Live Editor

Input

x
–
+
cmd
arr = [1,2,3,4], difference = 1

Output

x
–
+
cmd
4
Advertisements

Demonstration

Previous
#1217 Leetcode Minimum Cost to Move Chips to The Same Position Solution in C, C++, Java, JavaScript, Python, C# Leetcode
Next
#1219 Leetcode Path with Maximum Gold Solution in C, C++, Java, JavaScript, Python, C# Lee