/// <summary>
/// Merge two sorted arrays.
/// </summary>
private static void merge(Indexable <T> array, int leftStart, int middle, int rightEnd,
CustomComparer <T> comparer)
{
var newLength = rightEnd - leftStart + 1;
var result = new T[newLength];
int i = leftStart, j = middle + 1, k = 0;
//iteratively compare and pick min to result
while (i <= middle && j <= rightEnd)
{
if (comparer.Compare(array[i], array[j]) < 0)
{
result[k] = array[i];
i++;
}
else
{
result[k] = array[j];
j++;
}
k++;
}
//copy left overs
if (i <= middle)
{
for (var l = i; l <= middle; l++)
{
result[k] = array[l];
k++;
}
}
else
{
for (var l = j; l <= rightEnd; l++)
{
result[k] = array[l];
k++;
}
}
k = 0;
//now write back result
for (var g = leftStart; g <= rightEnd; g++)
{
array[g] = result[k];
k++;
}
}
internal static void PartitionMerge(Indexable <T> array, int leftIndex, int rightIndex,
CustomComparer <T> comparer)
{
if (leftIndex < 0 || rightIndex < 0 || (rightIndex - leftIndex + 1) < 2)
{
return;
}
var middle = (leftIndex + rightIndex) / 2;
PartitionMerge(array, leftIndex, middle, comparer);
PartitionMerge(array, middle + 1, rightIndex, comparer);
merge(array, leftIndex, middle, rightIndex, comparer);
}
/// <summary>
/// Time complexity: O(nlog(n)).
/// </summary>
public static Indexable <T> Sort(Indexable <T> array, SortDirection sortDirection = SortDirection.Ascending)
{
PartitionMerge(array, 0, array.Length - 1, new CustomComparer <T>(sortDirection, Comparer <T> .Default));
return(array);
}
public SpanEnumerator(Indexable <T> span)
{
this.span = span;
index = -1;
}
