コード例 #1
0
ファイル: QuickSort.cs プロジェクト: dse418/ShaneRepository
        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];
        }