private static void UncoverColumn(ColumnHeader c)
{
// I have used variable names c, i and j here to make it easy to
// relate this code to the original "Dancing Links" paper.
for (var i = c.Up; i != c; i = i.Up)
for (var j = i.Left; j != i; j = j.Left)
j.ColumnHeader.RelinkNode(j);
c.RelinkColumnHeader();
}
private static void CoverColumn(ColumnHeader c)
{
c.UnlinkColumnHeader();
// I have used variable names c, i and j here to make it easy to
// relate this code to the original "Dancing Links" paper.
for (var i = c.Down; i != c; i = i.Down)
for (var j = i.Right; j != i; j = j.Right)
j.ColumnHeader.UnlinkNode(j);
}
private void BuildInternalStructure(bool[,] matrix)
{
var numRows = matrix.GetLength(0);
var numCols = matrix.GetLength(1);
Root = new ColumnHeader();
for (var colIndex = 0; colIndex < numCols; colIndex++)
{
var columnHeader = new ColumnHeader();
Root.AppendColumnHeader(columnHeader);
}
for (var rowIndex = 0; rowIndex < numRows; rowIndex++)
{
// We are starting a new row so indicate that this row is currently empty.
Node lastNodeInThisRow = null;
for (var colIndex = 0; colIndex < numCols; colIndex++)
{
// We are only interested in the '1's ('true's) in the matrix.
// We create a node for each '1'. We ignore all the '0's ('false's).
if (!matrix[rowIndex, colIndex]) continue;
// Add the node to the appropriate column header.
var columnHeader = FindColumnHeader(colIndex);
var node = new Node(columnHeader, rowIndex);
// Append this node to the last node in this row (if there is one).
if (lastNodeInThisRow != null)
lastNodeInThisRow.AppendRowNode(node);
// This node is now the last node in this row.
lastNodeInThisRow = node;
}
}
}