<h2 id="heading-url">URL</h2>
<p><a target="_blank" href="https://leetcode.com/problems/permutation-in-string/description/">https://leetcode.com/problems/permutation-in-string/description/</a></p>
<h2 id="heading-code">Code</h2>
<p><a target="_blank" href="https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/challenge/202302/permutation_in_string/main.fsx">https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/challenge/202302/permutation_in_string/main.fs</a></p>
<pre><code class="lang-plaintext">let checkInclusion (s1: string) (s2: string) : bool =
    let toFreq (s: char list) : int [] =
        s
        |&gt; List.fold
            (fun (acc: int []) c -&gt;
                let index = int c - int 'a'
                acc.[index] &lt;- acc.[index] + 1
                acc)
            (Array.zeroCreate 26)

    if s1.Length &gt; s2.Length then
        false
    else
        let freq1 = toFreq (Seq.toList s1)

        s2
        |&gt; Seq.toList
        |&gt; List.windowed s1.Length
        |&gt; List.map toFreq
        |&gt; List.contains freq1
</code></pre>


## URL

[https://leetcode.com/problems/permutation-in-string/description/](https://leetcode.com/problems/permutation-in-string/description/)

## Code

[https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/challenge/202302/permutation\_in\_string/main.fs](https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/challenge/202302/permutation_in_string/main.fsx)

```plaintext
let checkInclusion (s1: string) (s2: string) : bool =
    let toFreq (s: char list) : int [] =
        s
        |> List.fold
            (fun (acc: int []) c ->
                let index = int c - int 'a'
                acc.[index] <- acc.[index] + 1
                acc)
            (Array.zeroCreate 26)

    if s1.Length > s2.Length then
        false
    else
        let freq1 = toFreq (Seq.toList s1)

        s2
        |> Seq.toList
        |> List.windowed s1.Length
        |> List.map toFreq
        |> List.contains freq1
```

LeetCode 567. Permutation in String in F#

URL

Code