2025-08-21 08:29:38 +0000 UTC

class Solution:
    def longestSubsequence(self, arr: List[int], difference: int) -> int:
        n = len(arr)
        freqs = defaultdict(list)
        for i, num in enumerate(arr):
            freqs[num].append(i)
        dp = [1] * n
        for i in reversed(range(n - 1)):
            cur, nxt = arr[i], arr[i] + difference
            if nxt not in freqs:
                continue
            cnt = 0
            for j in freqs[nxt]:
                if j > i:
                    cnt = max(cnt, dp[j])
            dp[i] = cnt + 1
        return max(dp)