/// <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 TestCopy()
{
var cpb = new CPBoard(bSolvableByCP);
CPBoard copy = cpb.Copy();
// Changing original does not mutate copy
Assert.NotEqual("4", copy.Get(0));
cpb.Set(0, "4");
Assert.NotEqual("4", copy.Get(0));
// Chaning copy does not change original
Assert.NotEqual("2", cpb.Get(1));
copy.Set(1, "2");
Assert.NotEqual("2", cpb.Get(1));
}