Esempio n. 1
0
GoLadderStatus GoLadderUtil::LadderStatus(const GoBoard& bd, SgPoint prey,
                                          bool twoLibIsEscape,
                                          SgPoint* toCapture,
                                          SgPoint* toEscape)
{
    SG_ASSERT(bd.IsValidPoint(prey));
    SG_ASSERT(bd.Occupied(prey));
#ifndef NDEBUG
    SgHashCode oldHash = bd.GetHashCode();
#endif
    // Unsettled only if can capture when hunter plays first, and can escape
    // if prey plays first.
    GoLadder ladder;
    SgBlackWhite preyColor = bd.GetStone(prey);
    SgVector<SgPoint> captureSequence;
    GoLadderStatus status = GO_LADDER_ESCAPED;
    if (ladder.Ladder(bd, prey, SgOppBW(preyColor), &captureSequence,
                      twoLibIsEscape) < 0)
    {
        SgVector<SgPoint> escapeSequence;
        if (ladder.Ladder(bd, prey, preyColor, &escapeSequence,
                          twoLibIsEscape) < 0)
            status = GO_LADDER_CAPTURED;
        else
        {
            status = GO_LADDER_UNSETTLED;
            // Unsettled = ladder depends on who plays first, so there must
            // be a move that can be played.
            SG_ASSERT(captureSequence.NonEmpty());
            // escapeSequence can be empty in 2 libs, prey to play case
            SG_ASSERT(twoLibIsEscape || escapeSequence.NonEmpty());
            if (toCapture)
                *toCapture = captureSequence.Front();
            if (toEscape)
                *toEscape = escapeSequence.IsEmpty() ? SG_PASS :
                                                       escapeSequence.Front();
        }
    }
#ifndef NDEBUG
    // Make sure Ladder didn't change the board position.
    SG_ASSERT(oldHash == bd.GetHashCode());
#endif
    return status;
}
Esempio n. 2
0
SgPoint GoLadderUtil::TryLadder(const GoBoard& bd, SgPoint prey,
                                SgBlackWhite firstPlayer)
{
    SgVector<SgPoint> sequence;
    bool isCaptured = Ladder(bd, prey, firstPlayer, true, &sequence);
    // if move is same color as prey, we want to escape
    // else we want to capture.
    SgPoint p;
    if (isCaptured != (firstPlayer == bd.GetStone(prey)))
        p = sequence.IsEmpty() ? SG_PASS : sequence.Front();
    else
        p = SG_NULLMOVE;
    return p;
}