/// <summary>
/// Array optimized
/// source.Distinct().ToArray()
/// </summary>
public static unsafe T[] DistinctToArray <T, TComp>(this T[] source)
where TComp : struct, IEqualityComparer <T>
{
var len = PowerOf2(source.Length * 2);
var buckets = stackalloc int[len];
var set = new StackHashSet <T, TComp>(source, buckets, len);
var resultIndexes = stackalloc int[source.Length];
var count = 0;
for (int i = 0; i < source.Length; i++)
{
if (!set.Add(source[i], i))
{
resultIndexes[count++] = i;
}
}
return(ToArray(source, resultIndexes, count));
}
/// <summary>
/// Array optimized
/// first.Except(second).ToArray()
/// </summary>
public static unsafe T[] ExceptToArray <T, TComp>(this T[] first, T[] second)
where TComp : struct, IEqualityComparer <T>
{
var len = PowerOf2(second.Length * 2);
var buckets = stackalloc int[len];
var set = new StackHashSet <T, TComp>(second, buckets, len);
set.MakeHashtTable();
var resultIndexes = stackalloc int[first.Length];
var count = 0;
for (int i = 0; i < first.Length; i++)
{
if (!set.Contains(first[i]))
{
resultIndexes[count++] = i;
}
}
return(ToArray(first, resultIndexes, count));
}
