public static bool Validate(Game game, int line, int column, int value)
{
if (value < 1 || value > 9)
{
return(false);
}
if (!game.IsEmpty(line, column))
{
return(false);
}
var possibilities = GetLinePossibilities(game, line)
.Intersect(GetColumnPossibilities(game, column))
.Intersect(GetSquarePossibilities(game, line, column));
return(possibilities.Contains(value));
}
public static bool Backtrack(Game game)
{
if (game.IsComplete())
{
return(true);
}
for (var i = 0; i < 9; i++)
{
for (var j = 0; j < 9; j++)
{
if (game.IsEmpty(i, j))
{
var possibilities = GetLinePossibilities(game, i)
.Intersect(GetColumnPossibilities(game, j))
.Intersect(GetSquarePossibilities(game, i, j));
foreach (var possibility in possibilities)
{
game.Set(i, j, possibility);
var result = Backtrack(game);
if (result == true)
{
return(true);
}
}
game.EmptyUp(i, j);
return(false);
}
}
}
return(false);
}