<h2 id="heading-url">URL</h2>
<a target="_blank" href="https://leetcode.com/problems/count-prefix-and-suffix-pairs-i/description/?envType=daily-question&amp;envId=2025-01-08">Count Prefix and Suffix Pairs I - LeetCode</a>
<h2 id="heading-code">Code</h2>
<a target="_blank" href="https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/challenge/202501/count_prefix_and_suffix_pairs1/main.fsx">https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/challenge/202501/count_prefix_and_suffix_pairs1/main.fsx</a>
<pre><code class="lang-fsharp">let countPrefixSuffixPairs (words: string list) : int =
 let isPrefixAndSuffix (str1: string) (str2: string) : bool =
 str2.StartsWith(str1) &amp;&amp; str2.EndsWith(str1)

 let rec countPrefixSuffixPairs' words acc =
 match words with
 | [] -&gt; acc
 | h :: t -&gt;
 let n = List.filter (fun s -&gt; isPrefixAndSuffix h s) t |&gt; List.length
 countPrefixSuffixPairs' t (acc + n)
</code></pre>

## URL

[Count Prefix and Suffix Pairs I - LeetCode](https://leetcode.com/problems/count-prefix-and-suffix-pairs-i/description/?envType=daily-question&envId=2025-01-08)

## Code

[https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/challenge/202501/count\_prefix\_and\_suffix\_pairs1/main.fsx](https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/challenge/202501/count_prefix_and_suffix_pairs1/main.fsx)

```fsharp
let countPrefixSuffixPairs (words: string list) : int =
    let isPrefixAndSuffix (str1: string) (str2: string) : bool =
        str2.StartsWith(str1) && str2.EndsWith(str1)

    let rec countPrefixSuffixPairs' words acc =
        match words with
        | [] -> acc
        | h :: t ->
            let n = List.filter (fun s -> isPrefixAndSuffix h s) t |> List.length
            countPrefixSuffixPairs' t (acc + n)
```

LeetCode 3042. Count Prefix and Suffix Pairs I in F#

URL

Code