private static void VecSwap(GenericSortArray x, int a, int b, int n)
{
for (int i = 0; i < n; i++, a++, b++)
{
x.Swap(a, b);
}
}
private static void Sort1(GenericSortArray x, int off, int len)
{
// Insertion sort on smallest arrays
if (len < 7)
{
for (int i = off; i < len + off; i++)
{
for (int j = i; j > off && x.Compare(j - 1, j) > 0; j--)
{
x.Swap(j, j - 1);
}
}
return;
}
// Choose a partition element, v
int m = off + (len >> 1); // Small arrays, middle element
if (len > 7)
{
int l = off;
int n = off + len - 1;
if (len > 40)
{
// Big arrays, pseudomedian of 9
int s = len / 8;
l = Med3(x, l, l + s, l + 2 * s);
m = Med3(x, m - s, m, m + s);
n = Med3(x, n - 2 * s, n - s, n);
}
m = Med3(x, l, m, n); // Mid-size, med of 3
}
// Establish Invariant: v* (<v)* (>v)* v*
int a = off, b = a, c = off + len - 1, d = c, diff;
while (true)
{
while (b <= c && (diff = x.Compare(b, m)) <= 0)
{
if (diff == 0)
{
x.Swap(a++, b);
}
b++;
}
while (c >= b && (diff = x.Compare(c, m)) >= 0)
{
if (diff == 0)
{
x.Swap(c, d--);
}
c--;
}
if (b > c)
{
break;
}
x.Swap(b++, c--);
}
// Swap partition elements back to middle
int s2, n2 = off + len;
s2 = System.Math.Min(a - off, b - a); VecSwap(x, off, b - s2, s2);
s2 = System.Math.Min(d - c, n2 - d - 1); VecSwap(x, b, n2 - s2, s2);
// Recursively sort non-partition-elements
if ((s2 = b - a) > 1)
{
Sort1(x, off, s2);
}
if ((s2 = d - c) > 1)
{
Sort1(x, n2 - s2, s2);
}
}
internal static void Sort(GenericSortArray arr)
{
Sort1(arr, 0, arr.Size());
}
private static int Med3(GenericSortArray x, int a, int b, int c)
{
return (x.Compare(a, b) < 0 ? (x.Compare(b, c) < 0 ? b : (x.Compare(a, c) < 0 ? c : a)) : (x.Compare(b, c) > 0 ? b : (x.Compare(a, c) > 0 ? c : a)));
}
