<h2 id="heading-url">URL</h2>
<p><a href="https://leetcode.com/problems/find-the-duplicate-number/" class="autolinkedURL autolinkedURL-url" target="_blank">leetcode.com/problems/find-the-duplicate-nu..</a></p>
<h2 id="heading-code">Code</h2>
<p><a href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0287/main.fsx" class="autolinkedURL autolinkedURL-url" target="_blank">github.com/syohex/dotnet-study/blob/master/..</a></p>
<pre><code class="lang-fsharp">let findDuplicate (nums: int list) : int =
    let rec findDuplicate' (nums: int []) left right =
        if left &gt; right then
            left
        else
            let mid = left + ((right - left) / 2)

            let count =
                nums
                |&gt; Array.fold (fun acc n -&gt; if n &lt;= mid then acc + 1 else acc) 0

            if count &lt;= mid then
                findDuplicate' nums (mid + 1) right
            else
                findDuplicate' nums left (mid - 1)

    findDuplicate' (nums |&gt; Array.ofList) 1 (nums.Length - 1)
</code></pre>


## URL

https://leetcode.com/problems/find-the-duplicate-number/

## Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/0287/main.fsx

```fsharp
let findDuplicate (nums: int list) : int =
    let rec findDuplicate' (nums: int []) left right =
        if left > right then
            left
        else
            let mid = left + ((right - left) / 2)

            let count =
                nums
                |> Array.fold (fun acc n -> if n <= mid then acc + 1 else acc) 0

            if count <= mid then
                findDuplicate' nums (mid + 1) right
            else
                findDuplicate' nums left (mid - 1)

    findDuplicate' (nums |> Array.ofList) 1 (nums.Length - 1)
```

LeetCode 287. Find the Duplicate Number in F#

URL

Code