private void pivot(string[] entries)
{
//
// An odd sample size is chosen based on the log of the interval size.
// The median of a randomly chosen set of samples is then returned as
// an estimate of the true median.
//
var length = Right + 1 - Left;
var logLen = (Int32)Math.Log10(length);
var pivotSamples = 2 * logLen + 1;
var sampleSize = Math.Min(pivotSamples, length);
var last = Left + sampleSize - 1;
// Sample without replacement
for (var first = Left; first <= last; first++)
{
// Random sampling avoids pathological cases
var random = Random.Next(first, Right + 1);
Swap(entries, first, random);
}
InsertionSort.Sort(entries, Left, last);
Median = entries[Left + sampleSize / 2];
}
