/// <summary>
/// Makes a move on this Connect 4 board at the specified move position
/// </summary>
/// <param name="move">The move to make</param>
/// <returns>A reference to this Connect 4 board</returns>
public override Board MakeMove(Move move)
{
C4Move m = (C4Move)move;
//Make a move in the first available row in the column
for (int y = 0; y < Height; y++)
{
if (boardContents[m.X, y] == 0)
{
//Make the move on this board
boardContents[m.X, y] = CurrentPlayer;
//Set the y position of the move
m.SetY(y);
//If this move made a column full, remove this column from the list of possible moves
if (y == Height - 1)
{
possibleMoves.Remove(m);
}
//Determine if there is a winner
DetermineWinner(m);
//Swap out the current player
CurrentPlayer = NextPlayer;
//Call the MakeMove method on the Board base class, to save the last move made on this board
return(base.MakeMove(move));
}
}
//If there are no available rows, raise an exception
throw new InvalidMoveException("Tried to make a move in a full column");
}
/// <summary>
/// Equality override for a Connect 4 move <para/>
/// Two moves are equal if their x positions are equal
/// </summary>
/// <param name="obj">The other C4Move instance to compare this one too</param>
/// <returns>True if the objects are equal, false otherwise</returns>
public override bool Equals(object obj)
{
if (obj is C4Move)
{
C4Move other = (C4Move)obj;
return(other.X == X);
}
return(false);
}
/// <summary>
/// Determine if the current game is over <para/>
/// Uses knowledge of the last move to save computation time
/// </summary>
/// <param name="move">The last move made</param>
protected override void DetermineWinner(Move move)
{
//This method seems a bit confusing, but it is just changing the worst case number of win checks from 196 to 16
C4Move m = (C4Move)move;
//Get the current cells value
int currentCell;
//Check for a horizontal win
//Check 3 cells infront and behind of this cell to determine if there is a winner
for (int x = m.X; x >= m.X - 3 && x >= 0; x--)
{
currentCell = boardContents[x, m.Y];
if (x < Width - 3)
{
if (boardContents[x + 1, m.Y] == currentCell && boardContents[x + 2, m.Y] == currentCell && boardContents[x + 3, m.Y] == currentCell)
{
winner = CurrentPlayer;
return;
}
}
}
//Check for a vertical win
//Check 3 cells up and down from this cell to determine if there is a winner
for (int y = m.Y; y >= m.Y - 3 && y >= 0; y--)
{
currentCell = boardContents[m.X, y];
if (y < Height - 3)
{
if (boardContents[m.X, y + 1] == currentCell && boardContents[m.X, y + 2] == currentCell && boardContents[m.X, y + 3] == currentCell)
{
winner = CurrentPlayer;
return;
}
}
}
//Check for an upwards diagonal win
//Check 3 cells down and left and 3 cells up and right from this cell to determine if there is a winner
for (int y = m.Y, x = m.X; x >= m.X - 3 && y >= m.Y - 3 && x >= 0 && y >= 0; x--, y--)
{
currentCell = boardContents[x, y];
if (x < Width - 3 && y < Height - 3)
{
if (boardContents[x + 1, y + 1] == currentCell && boardContents[x + 2, y + 2] == currentCell && boardContents[x + 3, y + 3] == currentCell)
{
winner = CurrentPlayer;
return;
}
}
}
//Check for a downwards diagonal win
//Check 3 cells up and left and 3 cells down and right from this cell to determine if there is a winner
for (int y = m.Y, x = m.X; x >= m.X - 3 && y <= m.Y + 3 && x >= 0 && y < Height; x--, y++)
{
currentCell = boardContents[x, y];
if (x < Width - 3 && y > 2)
{
if (boardContents[x + 1, y - 1] == currentCell && boardContents[x + 2, y - 2] == currentCell && boardContents[x + 3, y - 3] == currentCell)
{
winner = CurrentPlayer;
return;
}
}
}
//If there are no possible moves left and there is still no winner, the game is a draw
if (possibleMoves.Count == 0)
{
winner = 0;
}
}