<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/fibonacci-number/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/fibonacci-number</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0509/main.fsx" class="autolinkedURL autolinkedURL-url" target="_blank">github.com/syohex/dotnet-study/blob/master/..</a></p>
<pre><code class="lang-fsharp">let fib (n: int) : int =
    let rec fib' n cache =
        match n with
        | 0 -&gt; 0, cache
        | 1 -&gt; 1, cache
        | _ -&gt;
            match Map.tryFind n cache with
            | Some (v) -&gt; v, cache
            | None -&gt;
                let ret', cache' = fib' (n - 1) cache
                let ret'', cache'' = fib' (n - 2) cache'
                let ret = ret' + ret''
                ret, Map.add n ret cache''

    fib' n Map.empty |&gt; fst
</code></pre>


## URL

https://leetcode.com/problems/fibonacci-number/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0509/main.fsx

```fsharp
let fib (n: int) : int =
    let rec fib' n cache =
        match n with
        | 0 -> 0, cache
        | 1 -> 1, cache
        | _ ->
            match Map.tryFind n cache with
            | Some (v) -> v, cache
            | None ->
                let ret', cache' = fib' (n - 1) cache
                let ret'', cache'' = fib' (n - 2) cache'
                let ret = ret' + ret''
                ret, Map.add n ret cache''

    fib' n Map.empty |> fst
```

LeetCode 509. Fibonacci Number in F#

URL

Code