public int ComputerMove(int player, int level)
{
int bestCol = -1;
int best = -30000;
// Simulate a drop in each of the columns
for (int currentCol = 0; currentCol < 7; currentCol++)
{
C4Engine tempState = Copy();
// If column is full, try a different column
if (tempState.DropPiece(player, currentCol) < 0)
{
continue;
}
// If this drop wins the game, then go here
if (tempState.IsWinner() == player)
{
bestCol = currentCol;
break;
}
// Otherwise, evaluate this move
var goodness = tempState.Evaluate(player, level, 1);
// If this move looks better than previous moves, remember it
if (goodness > best)
{
best = goodness;
bestCol = currentCol;
}
//If the move is equally good, make a random decision
if (goodness == best)
{
if (Rand() % 2 == 0)
{
bestCol = currentCol;
}
}
}
// Drop the piece in the best column
if (bestCol >= 0)
{
var row = DropPiece(player, bestCol);
if (row >= 0)
{
return(bestCol);
}
}
return(-1);
}
int Evaluate(int player, int level, int depth)
{
int best = -30000;
if (depth <= level)
{
for (int currentCol = 0; currentCol < 7; currentCol++)
{
C4Engine tempState = Copy();
if (tempState.DropPiece(OtherPlayer(player), currentCol) < 0)
{
continue;
}
int goodness;
if (tempState.IsWinner() == OtherPlayer(player))
{
goodness = 25000 - depth;
}
else
{
goodness = tempState.Evaluate(OtherPlayer(player), level, depth + 1);
}
if (goodness > best)
{
best = goodness;
}
}
// What's good for the other player is bad for this one
return(-best);
}
return(CalcScore(player) - CalcScore(OtherPlayer(player)));
}