// Initialise the forward checking algorithm
static void initialise_forwardchecking()
{
starttime = DateTime.Now;
// Make a new grid
currentGrid = new Sudoku_Grid();
// Add squares to the grid with their number, row and column
for (int i = 0; i < N; i++)
{
for (int j = 0; j < N; j++)
{
currentGrid.sudoku[i, j] = new Square();
currentGrid.sudoku[i, j].row = i;
currentGrid.sudoku[i, j].column = j;
currentGrid.sudoku[i, j].number = sudoku[i, j];
// Make a domain list of all the possible numbers a square can have if it is changeable
if (!unchangable[i, j])
{
currentGrid.sudoku[i, j].variables = new List <int>();
int size = 0;
for (int k = 1; k <= N; k++)
{
sudoku[i, j] = k;
if (!Violation(i, j))
{
currentGrid.sudoku[i, j].variables.Add(k);
size++;
}
}
// Reset the value
sudoku[i, j] = 0;
currentGrid.sudoku[i, j].domainSize = size;
}
}
}
currentGrid.ForwardCheck();
}
// Recursive backtracking method that uses forward checking with the most constraining variable
public void ForwardCheck()
{
// Check if the most constraining variable is empty
if (MCV == null)
{
// Create a new location with a high domain size
Location l = new Location();
l.size = 900;
//Check for each square in the sudoku which square has the lowest domainsize
foreach (Square s in sudoku)
{
if (!Program.unchangable[s.row, s.column])
{
if (s.domainSize <= l.size)
{
l.row = s.row;
l.column = s.column;
l.size = s.domainSize;
if (l.size == 1)
{
break;
}
}
}
}
// Assign the location to the most contraining variable
MCV = l;
}
// If the most constraining variable has a size of 900, the sudoku is solved and print the solution
if (MCV.size > 800)
{
//PrintSolution();
Program.sudokufc = sudoku;
Printer.print_sudoku();
return;
}
Program.recursivecalls++;
// Copy this grid to make changes in the child
child = new Sudoku_Grid();
child = Clone(this);
child.parent = this;
// Get location of most constraining square
int row = MCV.row;
int col = MCV.column;
// Check if index has exceeded the amount of variables there are
if (currentVariableIndex < sudoku[row, col].variables.Count)
{
int variable = sudoku[row, col].variables[currentVariableIndex];
// Set the square to this variable
child.sudoku[row, col].number = variable;
// If there are no empty domains move next with the child
if (child.MakeConsistent(row, col))
{
child.ForwardCheck();
}
// Else increase the variable index to try the next possible variable
else
{
currentVariableIndex++;
ForwardCheck();
}
}
// If it has exceeded the amount of variables go back to the parent
else
{
parent.currentVariableIndex++;
parent.ForwardCheck();
}
}