/// <summary>
/// Exhaustively try all possible values for the tiles, using constraints to
/// reduce the search space
/// </summary>
/// <param name="cpb"></param>
/// <param name="depth"></param> Parameter debugging and curiousity
/// <returns></returns>
static private SearchResult search(CPBoard cpb, int depth)
{
var freeTile = cpb.GetFreeTile();
// No free tile available
if (freeTile.Value == null)
{
return(new SearchResult(cpb, IsSolved(cpb)));
}
var possibleValues = freeTile.Value;
foreach (var c in possibleValues)
{
// Make a copy in case we reach contradiction and need to revert back
var copy = cpb.Copy();
bool didAssign = Assign(copy, freeTile.Key, c.ToString());
CDebug.Assert(copy.Get(freeTile.Key) != cpb.Get(freeTile.Key), "Original CPB mutated!");
if (didAssign)
{
SearchResult sr = search(copy, depth + 1);
if (sr.DidSolve)
{
return(sr);
}
}
}
return(new SearchResult(cpb, false));
}
public void TestFreeTile()
{
var cpb = new CPBoard(bSolvableByCP);
var ft = cpb.GetFreeTile();
Assert.Equal(0, ft.Key);
Assert.Equal("123456789", ft.Value); // No elimination has occured yet
cpb = new CPBoard(bSolved);
ft = cpb.GetFreeTile();
Assert.Equal(0, ft.Key); // TODO: Really need maybe type, 0 is not a good default
Assert.Null(ft.Value);
}