<h2 id="heading-url">URL</h2>
<p><a target="_blank" href="https://leetcode.com/problems/verifying-an-alien-dictionary/description/">Verifying an Alien Dictionary - 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/0953/main.fsx">https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0953/main.fsx</a></p>
<pre><code class="lang-plaintext">let sort (a: string) (b: string) (dict: Map&lt;char, int&gt;) : int =
    let rec sort' a b dict =
        match a, b with
        | [], [] -&gt; 0
        | _, [] -&gt; 1
        | [], _ -&gt; -1
        | h1 :: t1, h2 :: t2 -&gt;
            if h1 &lt;&gt; h2 then
                compare (Map.find h1 dict) (Map.find h2 dict)
            else
                sort' t1 t2 dict

    sort' (Seq.toList a) (Seq.toList b) dict

let isAlienSorted (words: string list) (order: string) : bool =
    let dict =
        order |&gt; Seq.indexed |&gt; Seq.fold (fun acc (i, c) -&gt; Map.add c i acc) Map.empty

    let sorted = List.sortWith (fun a b -&gt; sort a b dict) words
    words = sorted
</code></pre>


## URL

[Verifying an Alien Dictionary - LeetCode](https://leetcode.com/problems/verifying-an-alien-dictionary/description/)

## Code

[https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0953/main.fsx](https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/0953/main.fsx)

```plaintext
let sort (a: string) (b: string) (dict: Map<char, int>) : int =
    let rec sort' a b dict =
        match a, b with
        | [], [] -> 0
        | _, [] -> 1
        | [], _ -> -1
        | h1 :: t1, h2 :: t2 ->
            if h1 <> h2 then
                compare (Map.find h1 dict) (Map.find h2 dict)
            else
                sort' t1 t2 dict

    sort' (Seq.toList a) (Seq.toList b) dict

let isAlienSorted (words: string list) (order: string) : bool =
    let dict =
        order |> Seq.indexed |> Seq.fold (fun acc (i, c) -> Map.add c i acc) Map.empty

    let sorted = List.sortWith (fun a b -> sort a b dict) words
    words = sorted
```

LeetCode 953. Verifying an Alien Dictionary

URL

Code