Move MaxPlay(Connect4Board board, int depth, int alpha = int.MinValue, int beta = int.MaxValue)
{
if (depth == 0 || board.Done)
{
return new Move {
Column = -1, Score = board.EvalScore()
}
}
;
var maxMove = new Move {
Column = -1, Score = int.MinValue
};
var possibleColumns = board.GetAvailableColumns();
for (var i = 0; i < possibleColumns.Count; i++)
{
var col = possibleColumns[i];
var newBoard = board.GetNewState(BoardTile.CPU, col);
var nextMove = MinPlay(newBoard, depth - 1, alpha, beta);
if (maxMove.Column == -1 || nextMove.Score > maxMove.Score)
{
maxMove.Column = col;
maxMove.Score = nextMove.Score;
alpha = nextMove.Score;
}
if (alpha >= beta)
{
return(maxMove);
}
}
return(maxMove);
}
Move MinPlay(Connect4Board board, int depth, int alpha = int.MinValue, int beta = int.MaxValue)
{
if (depth == 0 || board.Done)
{
return new Move {
Column = -1, Score = board.EvalScore()
}
}
;
var minMove = new Move {
Column = -1, Score = int.MaxValue
};
var possibleColumns = board.GetAvailableColumns();
for (var i = 0; i < possibleColumns.Count; i++)
{
var col = possibleColumns[i];
var newBoard = board.GetNewState(BoardTile.Player, col);
var nextMove = MaxPlay(newBoard, depth - 1, alpha, beta);
if (minMove.Column == -1 || nextMove.Score < minMove.Score)
{
minMove.Column = col;
minMove.Score = nextMove.Score;
beta = nextMove.Score;
}
if (alpha >= beta)
{
return(minMove);
}
}
return(minMove);
}
}
