// Get or set an array value.
public int this[int row, int col]
{
get
{
// Find the entry.
IntArrayEntry entry = FindEntry(row, col, false);
// If we didn't find it, return the default value.
if (entry == null)
{
return(DefaultValue);
}
// Return the entry's value.
return(entry.Value);
}
set
{
// See if this is the default value.
if (value.Equals(DefaultValue))
{
// Remove the entry from the array.
DeleteEntry(row, col);
}
else
{
// Save the new value.
// Find the entry, creating it if necessary.
IntArrayEntry entry = FindEntry(row, col, true);
// Save the value.
entry.Value = value;
}
}
}
// Find the ArrayEntry for this column.
// If create is true, create the ArrayEntry if it doesn't exist.
private IntArrayEntry FindColumn(IntArrayEntry entry, int col, bool create)
{
// Find the entry before the required one.
IntArrayEntry before = FindColumnBefore(entry, col);
// If we found it, return it.
if ((before.NextEntry != null) && (before.NextEntry.ColumnNumber == col))
{
return(before.NextEntry);
}
// We didn't find it. See if we should create it.
if (create)
{
// Create the new ArrayEntry.
IntArrayEntry newEntry = new IntArrayEntry();
newEntry.ColumnNumber = col;
// Insert it in the row's column list.
newEntry.NextEntry = before.NextEntry;
before.NextEntry = newEntry;
// Return it.
return(newEntry);
}
// We didn't find it and shouldn't create it. Return null.
return(null);
}
// Find the ArrayEntry for this column.
private IntArrayEntry FindColumnBefore(IntArrayEntry entry, int col)
{
// Find the entry before the required one.
while ((entry.NextEntry != null) && (entry.NextEntry.ColumnNumber < col))
{
entry = entry.NextEntry;
}
// Return the ArrayRow before the row or null.
return(entry);
}
// Copy the entries starting at fromEntry into
// the destination entry list after toEntry.
private void CopyEntries(IntArrayEntry fromEntry, IntArrayEntry toEntry)
{
while (fromEntry != null)
{
toEntry.NextEntry = new IntArrayEntry();
toEntry = toEntry.NextEntry;
toEntry.ColumnNumber = fromEntry.ColumnNumber;
toEntry.Value = fromEntry.Value;
toEntry.NextEntry = null;
// Move to the next entry.
fromEntry = fromEntry.NextEntry;
}
}
// Add the entries in the two lists fromEntry1 and fromEntry2
// and save the sums in the destination entry list after toEntry.
private void AddEntries(IntArrayEntry fromEntry1, IntArrayEntry fromEntry2, IntArrayEntry toEntry)
{
// Repeat as long as either from list has items.
while ((fromEntry1 != null) && (fromEntry2 != null))
{
// Make the new result entry.
toEntry.NextEntry = new IntArrayEntry();
toEntry = toEntry.NextEntry;
toEntry.NextEntry = null;
// See which column number is smaller.
if (fromEntry1.ColumnNumber < fromEntry2.ColumnNumber)
{
// Copy the fromEntry1 entry.
toEntry.ColumnNumber = fromEntry1.ColumnNumber;
toEntry.Value = fromEntry1.Value;
fromEntry1 = fromEntry1.NextEntry;
}
else if (fromEntry2.ColumnNumber < fromEntry1.ColumnNumber)
{
// Copy the fromEntry2 entry.
toEntry.ColumnNumber = fromEntry2.ColumnNumber;
toEntry.Value = fromEntry2.Value;
fromEntry2 = fromEntry2.NextEntry;
}
else
{
// The column numbers are the same. Add both entries.
toEntry.ColumnNumber = fromEntry1.ColumnNumber;
toEntry.Value = fromEntry1.Value + fromEntry2.Value;
fromEntry1 = fromEntry1.NextEntry;
fromEntry2 = fromEntry2.NextEntry;
}
}
// Add the rest of the entries from the list that is not empty.
if (fromEntry1 != null)
{
CopyEntries(fromEntry1, toEntry);
}
if (fromEntry2 != null)
{
CopyEntries(fromEntry2, toEntry);
}
}
// Delete the indicated entry if it exists.
public void DeleteEntry(int row, int col)
{
// Find the row before the entry's row.
IntArrayRow rowBefore = FindRowBefore(row);
// If we didn't find the row, we're done.
IntArrayRow arrayRow = rowBefore.NextRow;
if ((arrayRow == null) || (arrayRow.RowNumber != row))
{
return;
}
// Find the entry before this entry's entry.
IntArrayEntry entryBefore = FindColumnBefore(arrayRow.RowSentinel, col);
IntArrayEntry arrayEntry = entryBefore.NextEntry;
// If we didn't find the entry, we're done.
if ((arrayEntry == null) || (arrayEntry.ColumnNumber != col))
{
return;
}
// Remove the entry from the row's list.
entryBefore.NextEntry = arrayEntry.NextEntry;
// arrayEntry.NextEntry = null;
// free(arrayEntry);
// If there are no more entries in the row, remove it.
IntArrayEntry arraySentinel = arrayRow.RowSentinel;
if (arraySentinel.NextEntry == null)
{
rowBefore.NextRow = arrayRow.NextRow;
// arrayRow.RowSentinel = null;
// free(arraySentinel);
// free(arrayRow);
}
}
