// Find the ArrayRow for this row.
// If create is true, create the ArrayRow if it doesn't exist.
private IntArrayRow FindRow(int row, bool create)
{
// Find the ArrayRow before the one we want.
IntArrayRow before = FindRowBefore(row);
// If we found it, return it.
if ((before.NextRow != null) && (before.NextRow.RowNumber == row))
{
return(before.NextRow);
}
// We didn't find it. See if we should create it.
if (create)
{
// Create the new ArrayRow.
IntArrayRow newRow = new IntArrayRow();
newRow.RowNumber = row;
// Insert it in the row list.
newRow.NextRow = before.NextRow;
before.NextRow = newRow;
// Create the row's sentinel.
newRow.RowSentinel = new IntArrayEntry();
newRow.RowSentinel.NextEntry = null;
// Return it.
return(newRow);
}
// We didn't find it and shouldn't create it. Return null.
return(null);
}
// Create the sentinels.
public SparseIntArray(int defaultValue)
{
// Save the default value.
DefaultValue = defaultValue;
// Create the row sentinel.
TopSentinel = new IntArrayRow();
TopSentinel.NextRow = null;
}
// Find the ArrayRow before this row.
private IntArrayRow FindRowBefore(int row)
{
// Start at the sentinel.
IntArrayRow arrayRow = TopSentinel;
// Find the row before the required one.
while ((arrayRow.NextRow != null) && (arrayRow.NextRow.RowNumber < row))
{
arrayRow = arrayRow.NextRow;
}
// Return the ArrayRow before the row or null.
return(arrayRow);
}
// Find the ArrayEntry for this row and column.
// If create is true, create the ArrayEntry if it doesn't exist.
private IntArrayEntry FindEntry(int row, int col, bool create)
{
// Find the entry's row.
IntArrayRow arrayRow = FindRow(row, create);
// If we didn't find it (or create it), return null.
if (arrayRow == null)
{
return(null);
}
// Find the entry in this row and return it.
return(FindColumn(arrayRow.RowSentinel, col, create));
}
// 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);
}
}
// Add two SparseArrays representing matrices.
public SparseIntArray Add(SparseIntArray other)
{
SparseIntArray result = new SparseIntArray(this.DefaultValue);
// Variables to move through all of the arrays.
IntArrayRow array1Row = this.TopSentinel.NextRow;
IntArrayRow array2Row = other.TopSentinel.NextRow;
IntArrayRow resultRow = result.TopSentinel;
while ((array1Row != null) && (array2Row != null))
{
// Make a new result row.
resultRow.NextRow = new IntArrayRow();
resultRow = resultRow.NextRow;
resultRow.RowSentinel = new IntArrayEntry();
resultRow.NextRow = null;
// See which input row has the smaller row number.
if (array1Row.RowNumber < array2Row.RowNumber)
{
// array1Row comes first. Copy its values into result.
resultRow.RowNumber = array1Row.RowNumber;
CopyEntries(array1Row.RowSentinel.NextEntry, resultRow.RowSentinel);
array1Row = array1Row.NextRow;
}
else if (array2Row.RowNumber < array1Row.RowNumber)
{
// array2Row comes first. Copy its values into result.
resultRow.RowNumber = array2Row.RowNumber;
CopyEntries(array2Row.RowSentinel.NextEntry, resultRow.RowSentinel);
array2Row = array2Row.NextRow;
}
else
{
// The row numbers are the same. Add their values.
resultRow.RowNumber = array1Row.RowNumber;
AddEntries(
array1Row.RowSentinel.NextEntry,
array2Row.RowSentinel.NextEntry,
resultRow.RowSentinel);
array1Row = array1Row.NextRow;
array2Row = array2Row.NextRow;
}
}
// Add any remaining rows.
if (array1Row != null)
{
// Make a new result row.
resultRow.NextRow = new IntArrayRow();
resultRow = resultRow.NextRow;
resultRow.RowNumber = array1Row.RowNumber;
resultRow.RowSentinel = new IntArrayEntry();
resultRow.NextRow = null;
CopyEntries(array1Row.RowSentinel.NextEntry, resultRow.RowSentinel);
}
if (array2Row != null)
{
// Make a new result row.
resultRow.NextRow = new IntArrayRow();
resultRow = resultRow.NextRow;
resultRow.RowNumber = array2Row.RowNumber;
resultRow.RowSentinel = new IntArrayEntry();
resultRow.NextRow = null;
CopyEntries(array2Row.RowSentinel.NextEntry, resultRow.RowSentinel);
}
return(result);
}
