C# Span Extensions. Distinct elements, Count of repetitions per element. Useful when count of elements is less than 300

SpanExtensions

using System;
using System.Collections.Generic;

namespace Utilities;

public static class SpanExtensions
{
    public static int Distinct<T>(this Span<T> items)
    {
        EqualityComparer<T> comparer = EqualityComparer<T>.Default;
        int count = items.Length;
        int lastNonDuplicate = 0;
        for (int i = 0; i < count; i++)
        {
            var item = items[i];
            for (int j = 0; j < lastNonDuplicate; j++)
                if (comparer.Equals(item, items[j]))
                    goto end;
            items[lastNonDuplicate++] = item;
        end:;
        }
        return lastNonDuplicate;
    }

    public static int CountRepetitions<T>(this ReadOnlySpan<T> items, Span<(T key, int count)> repeatCount)
    {
        EqualityComparer<T> comparer = EqualityComparer<T>.Default;
        int count = items.Length;
        int lastNonDuplicate = 0;
        for (int i = 0; i < count; i++)
        {
            var item = items[i];
            for (int j = 0; j < lastNonDuplicate; j++)
                if (comparer.Equals(item, repeatCount[j].key))
                {
                    repeatCount[j].count++;
                    goto end;
                }
            repeatCount[lastNonDuplicate++] = (item, 1);
            end:;
        }
        return lastNonDuplicate;
    }
}