<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/sort-characters-by-frequency/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/sort-characters-by-fr..</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0451/main.fsx" class="autolinkedURL autolinkedURL-url" target="_blank">github.com/syohex/dotnet-study/blob/master/..</a></p>
<pre><code class="lang-fsharp">let frequencySort (s: string) : string =
    s
    |&gt; Seq.fold
        (fun acc c -&gt;
            match Map.tryFind c acc with
            | Some (v) -&gt; Map.add c (v + 1) acc
            | None -&gt; Map.add c 1 acc)
        Map.empty
    |&gt; Map.toList
    |&gt; List.sortWith (fun (c1, n1) (c2, n2) -&gt;
        if n1 = n2 then
            compare c1 c2
        else
            compare n2 n1)
    |&gt; List.fold
        (fun acc (c, n) -&gt;
            seq { 1..n }
            |&gt; Seq.fold (fun acc2 _ -&gt; c :: acc2) acc)
        []
    |&gt; List.rev
    |&gt; System.String.Concat
</code></pre>


## URL

https://leetcode.com/problems/sort-characters-by-frequency/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0451/main.fsx

```fsharp
let frequencySort (s: string) : string =
    s
    |> Seq.fold
        (fun acc c ->
            match Map.tryFind c acc with
            | Some (v) -> Map.add c (v + 1) acc
            | None -> Map.add c 1 acc)
        Map.empty
    |> Map.toList
    |> List.sortWith (fun (c1, n1) (c2, n2) ->
        if n1 = n2 then
            compare c1 c2
        else
            compare n2 n1)
    |> List.fold
        (fun acc (c, n) ->
            seq { 1..n }
            |> Seq.fold (fun acc2 _ -> c :: acc2) acc)
        []
    |> List.rev
    |> System.String.Concat
```

LeetCode 451. Sort Characters By Frequency in F#

URL

Code