给你一个整数数组 arr 和一个整数 difference，请你找出 arr 中所有相邻元素之间的差等于给定 difference 的等差子序列，并返回其中最长的等差子序列的长度。

 

示例 1：

输入：arr = [1,2,3,4], difference = 1
输出：4
解释：最长的等差子序列是 [1,2,3,4]。
示例 2：

输入：arr = [1,3,5,7], difference = 1
输出：1
解释：最长的等差子序列是任意单个元素。
示例 3：

输入：arr = [1,5,7,8,5,3,4,2,1], difference = -2
输出：4
解释：最长的等差子序列是 [7,5,3,1]。
 

提示：

1 <= arr.length <= 10^5
-10^4 <= arr[i], difference <= 10^4

  def longestSubsequence(self, arr: List[int], difference: int) -> int:
        n = len(arr)
        res = 1
        for i in range(n):
            count = 1
            for j in range(i + 1, n):
                if arr[i] + difference * count == arr[j]:
                    count += 1

                if count > res:
                    res = count

        return res

#
# @lc app=leetcode.cn id=1218 lang=python3
#
# [1218] 最长定差子序列
#

# @lc code=start


class Solution:

    # 动态规划
    def longestSubsequence(self, arr: List[int], difference: int) -> int:
        n = len(arr)
        res = 1
        dp = {}
        for num in arr:
            dp[num] = 1
            if num - difference in dp:
                dp[num] = dp[num - difference] + 1

        return max(dp.values())

# @lc code=end