<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/binary-tree-right-side-view/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/binary-tree-right-sid..</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0199/main.fsx" class="autolinkedURL autolinkedURL-url" target="_blank">github.com/syohex/dotnet-study/blob/master/..</a></p>
<pre><code class="lang-fsharp">type Tree =
    | Leaf
    | Node of int * Tree * Tree

let rightSideView (root: Tree) : int list =
    let rec rightSideView' q ret =
        match q with
        | [] -&gt; ret |&gt; List.rev
        | _ -&gt;
            let q', v =
                q
                |&gt; List.fold
                    (fun (acc, prev) n -&gt;
                        match n with
                        | Leaf -&gt; acc, prev
                        | Node (v, left, right) -&gt;
                            match left, right with
                            | Leaf, Leaf -&gt; acc, v
                            | Node (_), Leaf -&gt; (left :: acc), v
                            | Leaf, Node (_) -&gt; (right :: acc), v
                            | Node (_), Node (_) -&gt; (right :: left :: acc), v)
                    ([], -1)

            rightSideView' (q' |&gt; List.rev) (v :: ret)
</code></pre>


## URL

https://leetcode.com/problems/binary-tree-right-side-view/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0199/main.fsx

```fsharp
type Tree =
    | Leaf
    | Node of int * Tree * Tree

let rightSideView (root: Tree) : int list =
    let rec rightSideView' q ret =
        match q with
        | [] -> ret |> List.rev
        | _ ->
            let q', v =
                q
                |> List.fold
                    (fun (acc, prev) n ->
                        match n with
                        | Leaf -> acc, prev
                        | Node (v, left, right) ->
                            match left, right with
                            | Leaf, Leaf -> acc, v
                            | Node (_), Leaf -> (left :: acc), v
                            | Leaf, Node (_) -> (right :: acc), v
                            | Node (_), Node (_) -> (right :: left :: acc), v)
                    ([], -1)

            rightSideView' (q' |> List.rev) (v :: ret)
```

LeetCode 199. Binary Tree Right Side View in F#

URL

Code