Function SolveSudoku(matrix(,) As Integer, hmatrix(,) As String) As Boolean
		Dim row As Integer, col As Integer, num As Integer, k As Integer, h As Integer, startrow As Integer, startcol As Integer, s As Integer, f As Integer
		Dim checkBlankSpaces As Boolean = False
		'Kandidaten je Matrix-Zelle, die nicht eine vorgegebene Zahl enthält, ermitteln
		For row = 0 To 8
			For col = 0 To 8
				'Zeileninfo
				If (hmatrix(row, col)).Length > 1 Then
					For k = 0 To 8
						If (hmatrix(row, k)).Length = 1 Then
							hmatrix(row, col) = hmatrix(row, col).Replace(hmatrix(row, k), "")
						End If
					Next
				End If
				If hmatrix(row, col).Length = 1 Then Exit For
				If (hmatrix(row, col)).Length = 0 Then
					MessageBox.Show("Rätsel nicht lösbar.")
					Exit Function
				End If
				'Spalteninfo
				If (hmatrix(row, col)).Length > 1 Then
					For k = 0 To 8
						If (hmatrix(k, col)).Length = 1 Then
							hmatrix(row, col) = hmatrix(row, col).Replace(hmatrix(k, col), "")
						End If
					Next
				End If
				If hmatrix(row, col).Length = 1 Then Exit For
				If (hmatrix(row, col)).Length = 0 Then
					MessageBox.Show("Rätsel nicht lösbar.")
					Exit Function
				End If
				'Quadratinfo
				If (hmatrix(row, col)).Length > 1 Then
					startrow = row - (row Mod 3)
					startcol = col - (col Mod 3)
					For h = startrow To startrow + 2
						For k = startcol To startcol + 2
							If (hmatrix(h, k)).Length = 1 Then
								hmatrix(row, col) = hmatrix(row, col).Replace(hmatrix(h, k), "")
							End If
						Next
					Next
				End If
				If hmatrix(row, col).Length = 1 Then Exit For
				If (hmatrix(row, col)).Length = 0 Then
					MessageBox.Show("Rätsel nicht lösbar.")
					Exit Function
				End If
			Next
		Next
		'     verify If sudoku Is already solved And If Not solved,
		'    get Next "blank" space position  
		For row = 0 To 8
			For col = 0 To 8
				If matrix(row, col) = UNASSIGNED Then
					checkBlankSpaces = True
					Exit For
				End If
			Next col
			If checkBlankSpaces = True Then
				Exit For
			End If
		Next row
		' no more "blank" spaces means the puzzle Is solved
		If checkBlankSpaces = False Then
			Return True
		End If
		'Try To fill "blank" space With correct num
		'anzahl schritte
		s = hmatrix(row, col).Length
		For f = 0 To s - 1
			num = CInt(hmatrix(row, col).Substring(f, 1))
			'isSafe checks that num isn't already present 
			'In the row, column, Or 3x3 box (see below)  
			If IsSafe(matrix, row, col, num) Then
				matrix(row, col) = num
				If SolveSudoku(matrix, hmatrix) = True Then
					Return True
				End If
				'If num Is placed In incorrect position, 
				'mark As "blank" again Then backtrack With 
				'a different num  
				matrix(row, col) = UNASSIGNED
			End If
		Next
		Return False
	End Function