public static int PartitionArray(int[] array, int beginIndex, int endIndex, QuickSortStatistics stats)
{
// assumptions: there are at least two elements in the input subarray
// invariant:
// all elements with index >= b are >= partition value (PV)
// all elements with index <= a are < PV
int partitionValue = array[endIndex];
int endLesserPartitionIndex = beginIndex - 1;
int currentIndex = beginIndex;
while (currentIndex < endIndex)
{
if (array[currentIndex] < partitionValue)
{
endLesserPartitionIndex++;
ArrayUtility.Swap(array, currentIndex, endLesserPartitionIndex);
stats.numSwaps++;
}
currentIndex++;
}
int partitionIndex = endLesserPartitionIndex + 1;
ArrayUtility.Swap(array, partitionIndex, endIndex);
stats.numSwaps++;
return(partitionIndex);
}
public static void Sort(int[] array, PartitionArrayFunc partitionFunc = null)
{
partitionFunc = partitionFunc ?? QuickSortClassicPartition.PartitionArray;
QuickSort.stats = new QuickSortStatistics();
if (array == null || array.Length <= 1)
{
// null, empty, and singleton arrays are already sorted
return;
}
QuickSortInternal(array, 0, array.Length - 1, partitionFunc);
}
public void QuicSort_SmallArray_ReturnRightComparesCount(string testCase)
{
IQuickSortWithStatistics[] quicSortVersions =
{
new QuickSortWithLastReferenceElement(),
new QuickSortWithFirstReferenceElement(),
new QuickSortWithCalculatedReferenceElement()
};
CompareCountTestData testData = CompareCountTestDataBuilder.CreateTestDate(testCase);
for (int i = 0; i < quicSortVersions.Length; i++)
{
IQuickSortWithStatistics quickSort = quicSortVersions[i];
QuickSortStatistics statistics = quickSort.Sort(testData.InputCollection);
Assert.That(statistics.ComparesCount, Is.EqualTo(testData.ExpectedCounts[i]));
Assert.That(statistics.SortedCollection, Is.Ordered);
}
}
public static int PartitionArray(int[] array, int beginIndex, int endIndex, QuickSortStatistics stats)
{
// assumptions: there are at least two elements in the input subarray
// invariant:
// all elements with index >= b are >= partition value (PV)
// all elements with index <= a are < PV
int partitionValueIndex = endIndex;
int partitionValue = array[partitionValueIndex];
int a = beginIndex - 1;
int b = endIndex - 1;
while (b > a + 1)
{
if (array[b] < partitionValue)
{
a++;
ArrayUtility.Swap(array, a, b);
stats.numSwaps++;
}
else
{
b--;
}
}
if (array[b] < partitionValue)
{
b++;
}
int tmp = array[b];
array[b] = partitionValue;
array[partitionValueIndex] = tmp;
stats.numSwaps++;
return(b);
}
