/// <summary>
/// Sorts elements in an order provided by the comparism method. Needs N log N operations. Worst case (already sorted) is something like 20% slower.
/// </summary>
/// <param name="count">Number of elements to sort (from indices 0 to count-1).</param>
/// <param name="compare">A compare method wich takes two indices and compares the elements at those indices.</param>
/// <param name="swap">A swap method which swaps the elements at two indices.</param>
private static void HeapSort(int count, RowComparismMethod compare, RowSwapMethod swap)
{
int N;
int k;
if (count == 0)
{
return; // No data to sort
}
/* We have n_data elements, last element is at 'n_data-1', first at
* '0' Set N to the last element number. */
N = count - 1;
k = N / 2;
k++; // Compensate the first use of 'k--'
do
{
k--;
downheap(N, k, compare, swap);
}while (k > 0);
while (N > 0)
{
// first swap the elements
swap(0, N);
// then process the heap
N--;
downheap(N, 0, compare, swap);
}
}
private static void downheap(int N, int k, RowComparismMethod CMP, RowSwapMethod swap)
{
while (k <= N / 2)
{
int j = 2 * k;
if (j < N && CMP(j, j + 1) < 0)
{
j++;
}
if (CMP(k, j) < 0)
{
swap(j, k);
}
else
{
break;
}
k = j;
}
}