<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/flatten-binary-tree-to-linked-list/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/flatten-binary-tree-t..</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0114/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 flatten (root: Tree) : Tree =
    let rec collectNodes node acc =
        match node with
        | Leaf -&gt; acc |&gt; List.rev
        | Node (v, left, right) -&gt;
            (collectNodes left (v :: acc))
            @ (collectNodes right [])

    let rec nodesToFlattenTree nodes =
        match nodes with
        | [] -&gt; Leaf
        | h :: t -&gt; Node(h, Leaf, nodesToFlattenTree t)

    collectNodes root [] |&gt; nodesToFlattenTree
</code></pre>


## URL

https://leetcode.com/problems/flatten-binary-tree-to-linked-list/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0114/main.fsx

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

let flatten (root: Tree) : Tree =
    let rec collectNodes node acc =
        match node with
        | Leaf -> acc |> List.rev
        | Node (v, left, right) ->
            (collectNodes left (v :: acc))
            @ (collectNodes right [])

    let rec nodesToFlattenTree nodes =
        match nodes with
        | [] -> Leaf
        | h :: t -> Node(h, Leaf, nodesToFlattenTree t)

    collectNodes root [] |> nodesToFlattenTree
```

LeetCode 114. Flatten Binary Tree to Linked List in F#

URL

Code