public bool DoesPlayer1HaveZugzwang(Board board)
{
//find threats, label even or odd
var boardSearch = new BoardSearch(4);
var groups = boardSearch.FindGroups(1, board, 1);
var hasOddThreat = groups.Select(g => g.Coords.Any(t => t.Row % 2 != 0)).Any();
return(hasOddThreat);
}
public int Run(Board board, int numToWin, int playerNumber = 2)
{
PLAYERNUM = playerNumber;
var search = new BoardSearch(numToWin);
var legalMoves = search.FindAllLegalMoves(board);
var yourThreats = search.FindGroups(PLAYERNUM, board, 1);
var oppThreats = search.FindGroups(1, board, 1);
int?columnToPlay = 0;
//can you win?
columnToPlay = MatchThreatsWithLegal(yourThreats, legalMoves);
if (columnToPlay.HasValue)
{
return(columnToPlay.Value);
}
//should you block?
columnToPlay = MatchThreatsWithLegal(oppThreats, legalMoves);
if (columnToPlay.HasValue)
{
return(columnToPlay.Value);
}
//are there hidden forks for player 1?
//look for threats with 2 blanks
var forkThreats = search.FindGroups(1, board, 2);
//do any threats share a blank?
var forkPositions = new List <Position>();
for (var i = 0; i < forkThreats.Count; i++)
{
var ft = forkThreats[i];
var blanks = ft.Coords.Where(c => c.Mark == 0);
for (var j = 0; j < forkThreats.Count; j++)
{
if (j == i)
{
continue;
}
var jft = forkThreats[j];
var jBlanks = jft.Coords.Where(c => c.Mark == 0);
var shared = jBlanks.Intersect <Position>(blanks, new PositionEqualityComparer());
forkPositions.AddRange(shared);
}
}
//are any blanks legal moves?
columnToPlay = MatchPositionsThreatsWithLegal(forkPositions, legalMoves);
if (columnToPlay.HasValue)
{
return(columnToPlay.Value);
}
//should we remove a legal move if it will harm us?
//can player1 score after this move?
//take all legal moves and transpose one row up - do any fulfill player 1 threats?
var toRemove = new List <Position>();
foreach (var legalMove in legalMoves)
{
var transposedMove = new Position(legalMove.Row + 1, legalMove.Col, 0);
foreach (var threat in oppThreats)
{
var blank = threat.Coords.Single(t => t.Mark == 0);
if (blank.Equals(transposedMove))
{
toRemove.Add(legalMove);
}
}
}
toRemove.ForEach(r => legalMoves.Remove(r));
//claimeven
var claimevens = search.FindPossibleClaimEvens(board);
foreach (var claimEven in claimevens)
{
foreach (var move in legalMoves)
{
if (claimEven == move.Col)
{
return(claimEven);
}
}
}
var moveIndex = random.Next(0, legalMoves.Count());
return(legalMoves[moveIndex].Col);
}