static void Main(string[] args)
{
Cell[,] board = new Cell [,]{
{new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(2, 1), new Cell(0, 0), new Cell(2, 8), new Cell(0, 0), new Cell(2, 3), new Cell(2, 2)},
{new Cell(2, 5), new Cell(2, 9), new Cell(0, 0), new Cell(0, 0), new Cell(2, 4), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0)},
{new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(2, 7), new Cell(0, 0), new Cell(0, 0), new Cell(2, 4), new Cell(0, 0), new Cell(0, 0)},
{new Cell(2, 9), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(2, 6), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0)},
{new Cell(2, 8), new Cell(0, 0), new Cell(2, 3), new Cell(0, 0), new Cell(2, 2), new Cell(0, 0), new Cell(2, 6), new Cell(0, 0), new Cell(2, 5)},
{new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(2, 4), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(2, 9)},
{new Cell(0, 0), new Cell(0, 0), new Cell(2, 7), new Cell(0, 0), new Cell(0, 0), new Cell(2, 4), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0)},
{new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0), new Cell(2, 3), new Cell(0, 0), new Cell(0, 0), new Cell(2, 8), new Cell(2, 4)},
{new Cell(2, 2), new Cell(2, 1), new Cell(0, 0), new Cell(2, 8), new Cell(0, 0), new Cell(2, 9), new Cell(0, 0), new Cell(0, 0), new Cell(0, 0)}};
Print(board);
Console.WriteLine();
if (Solve(board, 0, 0))
{
Console.WriteLine("Found a Solution!");
Print(board);
}
else
{
Console.WriteLine("No solution found");
}
}
public static bool Solve(Cell[,] board, int r, int c)
{
if (r == 9)
{
int count = 0;
for (int i = 0; i < 9; i++) // check to see if board is solved
{
for (int j = 0; j < 9; j++)
{
count += board[i, j].changable > 0 ? 1 : 0;
}
}
if (count == 81)
return true;
else
return false;
}
if (board[r, c].changable >= 1) // check to see if value is changable
{
int nextR = r;
int nextC = c + 1;
if (nextC == 9)
{
nextR = r + 1; nextC = 0;
}
return Solve(board, nextR, nextC); // if value is not changable send the next cell through solver
}
else
{
bool[] used = new bool[9];
for (int i = 0; i < 9; i++) // check row to see what values are used
{
if (board[r, i].changable >= 1)
used[board[r, i].val - 1] = true;
}
for (int i = 0; i < 9; i++) // check column to see what values are used
{
if (board[i, c].changable >= 1)
used[board[i, c].val - 1] = true;
}
for (int i = r - (r % 3); i < r - (r % 3) + 3; i++) // check box to see what values are used
{
for (int j = c - (c % 3); j < c - (c % 3) + 3; j++)
{
if (board[i, j].changable >= 1)
used[board[i, j].val - 1] = true;
}
}
for (int i = 0; i < used.Length; i++) // assign value to board
{
if (!used[i])
{
board[r, c].changable = 1;
board[r, c].val = i + 1;
int nextR = r;
int nextC = c + 1;
if (nextC == 9)
{
nextR = r + 1; nextC = 0;
}
if (Solve(board, nextR, nextC))
return true;
for (int m = 0; m < 9; m++)
for (int n = 0; n < 9; n++)
{
if (m > r || (m == r && n >= c))
{
if (board[m, n].changable == 1)
{
board[m, n].changable = 0;
board[m, n].val = 0;
}
}
}
}
}
}
return false;
}
public static void Print(Cell [,] board)
{
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
Console.Write( "{0} ", board[i,j].val);
}
Console.WriteLine();
}
}
