<h2 id="heading-url">URL</h2>
<p><a target="_blank" href="https://leetcode.com/problems/longest-arithmetic-subsequence-of-given-difference/description/">Longest Arithmetic Subsequence of Given Difference - LeetCode</a></p>
<h2 id="heading-code">Code</h2>
<p><a target="_blank" href="https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/1218/main.fsx">https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/1218/main.fsx</a></p>
<pre><code class="lang-plaintext">open System

let longestSubsequence (arr: int list) (difference: int) : int =
    arr
    |&gt; List.fold
        (fun (m, ret) n -&gt;
            match Map.tryFind (n - difference) m with
            | Some(v) -&gt; Map.add n (v + 1) m, Math.Max(ret, v + 1)
            | None -&gt; Map.add n 1 m, ret)
        (Map.empty, 1)
    |&gt; snd
</code></pre>


## URL

[Longest Arithmetic Subsequence of Given Difference - LeetCode](https://leetcode.com/problems/longest-arithmetic-subsequence-of-given-difference/description/)

## Code

[https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/1218/main.fsx](https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/1218/main.fsx)

```plaintext
open System

let longestSubsequence (arr: int list) (difference: int) : int =
    arr
    |> List.fold
        (fun (m, ret) n ->
            match Map.tryFind (n - difference) m with
            | Some(v) -> Map.add n (v + 1) m, Math.Max(ret, v + 1)
            | None -> Map.add n 1 m, ret)
        (Map.empty, 1)
    |> snd
```

LeetCode 1218. Longest Arithmetic Subsequence of Given Difference in F#

URL

Code