<h2 id="heading-url">URL</h2>
<p><a target="_blank" href="https://leetcode.com/problems/peak-index-in-a-mountain-array/description/">Peak Index in a Mountain Array - LeetCode</a></p>
<h2 id="heading-code">Code</h2>
<p><a target="_blank" href="https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0852/main.fsx">https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0852/main.fsx</a></p>
<pre><code class="lang-plaintext">let peakIndexInMountainArray (arr: int list) : int =
    let rec peakIndexInMountainArray' (arr: int[]) left right =
        if left &gt;= right then
            left
        else
            let mid = left + (right - left) / 2

            if arr.[mid] &lt; arr.[mid + 1] then
                peakIndexInMountainArray' arr (mid + 1) right
            else
                peakIndexInMountainArray' arr left mid

    let arr' = Array.ofList arr
    peakIndexInMountainArray' arr' 0 (arr.Length - 1)
</code></pre>


## URL

[Peak Index in a Mountain Array - LeetCode](https://leetcode.com/problems/peak-index-in-a-mountain-array/description/)

## Code

[https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0852/main.fsx](https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0852/main.fsx)

```plaintext
let peakIndexInMountainArray (arr: int list) : int =
    let rec peakIndexInMountainArray' (arr: int[]) left right =
        if left >= right then
            left
        else
            let mid = left + (right - left) / 2

            if arr.[mid] < arr.[mid + 1] then
                peakIndexInMountainArray' arr (mid + 1) right
            else
                peakIndexInMountainArray' arr left mid

    let arr' = Array.ofList arr
    peakIndexInMountainArray' arr' 0 (arr.Length - 1)
```

LeetCode 852. Peak Index in a Mountain Array in F#

URL

Code