// Function for 3-way merge sort process
public static void mergeSort3Way(MyFileArray gArray)
{
// if array of size is zero returns null
if (gArray == null)
{
return;
}
// creating duplicate of given array
// copying elements of given array into
// duplicate array
MyFileArray fArray = new MyFileArray(@"mydataarraycopy.dat", gArray);
// sort function
mergeSort3WayRec(fArray, 0, gArray.Length, gArray);
// copy back elements of duplicate array
// to given array
for (int i = 0; i < fArray.Length; i++)
{
gArray.Replace(i, fArray[i]);
}
fArray.fs.Close();
File.Delete(@"mydataaarraycopy.dat");
}
/* Merge the sorted ranges [low, mid1), [mid1,
* mid2) and [mid2, high) mid1 is first midpoint
* index in overall range to merge mid2 is second
* midpoint index in overall range to merge*/
public static void merge(MyFileArray gArray, int low,
int mid1, int mid2, int high,
MyFileArray destArray)
{
int i = low, j = mid1, k = mid2, l = low;
// choose smaller of the smallest in the three ranges
while ((i < mid1) && (j < mid2) && (k < high))
{
if (gArray[i].CompareTo(gArray[j]) < 0)
{
if (gArray[i].CompareTo(gArray[k]) < 0)
{
destArray.Replace(l++, gArray[i++]);
}
else
{
destArray.Replace(l++, gArray[k++]);
}
}
else
{
if (gArray[j].CompareTo(gArray[k]) < 0)
{
destArray.Replace(l++, gArray[j++]);
}
else
{
destArray.Replace(l++, gArray[k++]);
}
}
}
// case where first and second ranges have
// remaining values
while ((i < mid1) && (j < mid2))
{
if (gArray[i].CompareTo(gArray[j]) < 0)
{
destArray.Replace(l++, gArray[i++]);
}
else
{
destArray.Replace(l++, gArray[j++]);
}
}
// case where second and third ranges have
// remaining values
while ((j < mid2) && (k < high))
{
if (gArray[j].CompareTo(gArray[k]) < 0)
{
destArray.Replace(l++, gArray[j++]);
}
else
{
destArray.Replace(l++, gArray[k++]);
}
}
// case where first and third ranges have
// remaining values
while ((i < mid1) && (k < high))
{
if (gArray[i].CompareTo(gArray[k]) < 0)
{
destArray.Replace(l++, gArray[i++]);
}
else
{
destArray.Replace(l++, gArray[k++]);
}
}
// copy remaining values from the first range
while (i < mid1)
{
destArray.Replace(l++, gArray[i++]);
}
// copy remaining values from the second range
while (j < mid2)
{
destArray.Replace(l++, gArray[j++]);
}
// copy remaining values from the third range
while (k < high)
{
destArray.Replace(l++, gArray[k++]);
}
}
