func (b *Board) genSparseMatrix(root *dlx.Node) {
sideLen := b.sideLen()
nCells := sideLen * sideLen
nConstraints := nCells * 4
headers := make([]*dlx.Node, nConstraints)
row := make([]*dlx.Node, 4)
rowOffset := sideLen * sideLen
colOffset := rowOffset * 2
blkOffset := rowOffset * 3
for i := range headers {
headers[i] = dlx.AddHeader(root)
}
for r := 0; r < sideLen; r++ {
for c := 0; c < sideLen; c++ {
for v := 0; v < sideLen; v++ {
poss := b.possibility(r, c, v)
row[0] = dlx.AddNode(poss, headers[r*sideLen+c])
row[1] = dlx.AddNode(poss, headers[rowOffset+r*sideLen+v])
row[2] = dlx.AddNode(poss, headers[colOffset+c*sideLen+v])
row[3] = dlx.AddNode(poss, headers[blkOffset+
(r/b.blockRows*b.blockCols+c/b.blockCols)*sideLen+v])
err := dlx.BuildRow(row)
if err != nil {
log.Fatal("sudoku: could not attach a row")
}
}
}
}
}
func genSparseMatrix(root *dlx.Node) {
var headers [maxCols]*dlx.Node
row := make([]*dlx.Node, 4)
for i := range headers {
headers[i] = dlx.AddHeader(root)
}
for r := 0; r < gridLen; r++ {
for c := 0; c < gridLen; c++ {
for v := 0; v < gridLen; v++ {
poss := possibility(r, c, v)
row[0] = dlx.AddNode(poss, headers[r*gridLen+c])
row[1] = dlx.AddNode(poss, headers[rowConstraintsOff+r*gridLen+v])
row[2] = dlx.AddNode(poss, headers[colConstraintsOff+c*gridLen+v])
row[3] = dlx.AddNode(poss, headers[blkConstraintsOff+
(r/blockLen+c/blockLen*blockLen)*gridLen+v])
dlx.BuildRow(row)
}
}
}
}