<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/3sum-with-multiplicity/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/3sum-with-multiplicity</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0923/main.fsx" class="autolinkedURL autolinkedURL-url" target="_blank">github.com/syohex/dotnet-study/blob/master/..</a></p>
<pre><code class="lang-fsharp">let threeSumMulti (arr: int list) (target: int) : int =
    let rec threeSumMulti' arr target m ret =
        match arr with
        | [] -&gt; ret
        | h :: t -&gt;
            let ret' =
                t
                |&gt; List.fold
                    (fun acc n -&gt;
                        let diff = target - h - n

                        match Map.tryFind diff m with
                        | Some (v) -&gt; (acc + v) % 1_000_000_007
                        | None -&gt; acc)
                    ret

            let m' =
                match Map.tryFind h m with
                | Some (v) -&gt; Map.add h (v + 1) m
                | None -&gt; Map.add h 1 m

            threeSumMulti' t target m' ret'

    threeSumMulti' arr target Map.empty 0
</code></pre>


## URL

https://leetcode.com/problems/3sum-with-multiplicity/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0923/main.fsx

```fsharp
let threeSumMulti (arr: int list) (target: int) : int =
    let rec threeSumMulti' arr target m ret =
        match arr with
        | [] -> ret
        | h :: t ->
            let ret' =
                t
                |> List.fold
                    (fun acc n ->
                        let diff = target - h - n

                        match Map.tryFind diff m with
                        | Some (v) -> (acc + v) % 1_000_000_007
                        | None -> acc)
                    ret

            let m' =
                match Map.tryFind h m with
                | Some (v) -> Map.add h (v + 1) m
                | None -> Map.add h 1 m

            threeSumMulti' t target m' ret'

    threeSumMulti' arr target Map.empty 0
```

LeetCode 923. 3Sum With Multiplicity in F#

URL

Code