<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/binary-search-tree-iterator/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/binary-search-tree-it..</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0173/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

type BSTIterator =
    { Nums: int []
      mutable Index: int }

    static member New(root: Tree) : BSTIterator =
        let rec collect node acc =
            match node with
            | Leaf -&gt; acc
            | Node (n, left, right) -&gt;
                let acc' = collect left acc
                collect right (n :: acc')

        let nums =
            collect root [] |&gt; List.rev |&gt; List.toArray

        { Nums = nums; Index = 0 }

    member this.Next() : int =
        let ret = this.Nums.[this.Index]
        this.Index &lt;- this.Index + 1
        ret

    member this.HasNext() : bool = this.Index &lt; this.Nums.Length
</code></pre>
<p>This problem is not suit for F#</p>


## URL

https://leetcode.com/problems/binary-search-tree-iterator/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0173/main.fsx

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

type BSTIterator =
    { Nums: int []
      mutable Index: int }

    static member New(root: Tree) : BSTIterator =
        let rec collect node acc =
            match node with
            | Leaf -> acc
            | Node (n, left, right) ->
                let acc' = collect left acc
                collect right (n :: acc')

        let nums =
            collect root [] |> List.rev |> List.toArray

        { Nums = nums; Index = 0 }

    member this.Next() : int =
        let ret = this.Nums.[this.Index]
        this.Index <- this.Index + 1
        ret

    member this.HasNext() : bool = this.Index < this.Nums.Length
```

This problem is not suit for F#

LeetCode 173. Binary Search Tree Iterator in F#

URL

Code