public int MiniMax(GameState gs, int depth, Boolean maxPlayer)
{
//base case
if (depth == 0 || gs.GetState().Equals(GameState.State.terminal))
{
return FindHeuristicValue(gs);
}
if(maxPlayer)
{
int bestValue = MIN_VALUE;
foreach(GameState child in gs.GetChildren())
{
int value = MiniMax(child, depth - 1, false);
if (value.CompareTo(bestValue) > 0)
{
gs.SetHeuristicValue(value);
bestValue = value;
}
}
return bestValue;
}
else
{
int bestValue = MAX_VALUE;
foreach (GameState child in gs.GetChildren())
{
int value = MiniMax(child, depth - 1, true);
if(value.CompareTo(bestValue) < 0)
{
gs.SetHeuristicValue(value);
bestValue = value;
}
}
return bestValue;
}
}
public int FindHeuristicValue(GameState gs)
{
int value = 0;
//The count of connectCells a cell contains
int bestCount = 0;
int connectR = Board.GetConnectR();
if(gs.GetState().Equals(GameState.State.terminal))
{
return gs.GetHeuristicValue();
}
//if true it is maxPlayers turn and the board needs to be evaluate to minimize min's score
if(gs.isMaxPlayer())
{
//check if max can make a killer move
foreach(Cell cell in gs.GetBoard().getPlayerCells(gs.GetPlayer()))
{
if(cell.isTerminal() > 0)
{
value = MAX_VALUE;
return value;
}
}
//check if it is impossible to prevent min from winning
if(gs.GetCell().isTerminal() > 1)
{
value = MIN_VALUE;
return value;
}
//check if min can make a killer move
foreach (Cell cell in gs.GetBoard().getPlayerCells(gs.GetPlayer().getOpponent()))
{
if (cell.isTerminal() == 1)
{
value = MIN_VALUE / 2;
return value;
}
}
//last resort - find the move that gives the most possibilites for connect 4
foreach(Cell cell in gs.GetBoard().getPlayerCells(gs.GetPlayer()))
{
int count = 0;
foreach(KeyValuePair<int, HashSet<Cell>> c in cell.GetObservers())
{
count = count + c.Value.Count;
}
foreach(KeyValuePair<int, List<Cell>> k in cell.GetConnectedCells())
{
count = count + k.Value.Count;
}
if(count > bestCount)
{
bestCount = count;
}
}
value = bestCount;
return value;
}
//It is not max's turn
else
{
//check if min can make a killer move
foreach (Cell cell in gs.GetBoard().getPlayerCells(gs.GetPlayer().getOpponent()))
{
if (cell.isTerminal() > 0)
{
value = MIN_VALUE;
return value;
}
}
//check if it is impossible to prevent max from winning
if (gs.GetCell().isTerminal() > 1)
{
value = MAX_VALUE;
return value;
}
//check if max can make a killer move
foreach (Cell cell in gs.GetBoard().getPlayerCells(gs.GetPlayer()))
{
if (cell.isTerminal() == 1)
{
value = MAX_VALUE / 2;
return value;
}
}
}
//last resort - find the move that gives the most possibilites for connect 4
foreach (Cell cell in gs.GetBoard().getPlayerCells(gs.GetPlayer().getOpponent()))
{
int count = 0;
foreach (KeyValuePair<int, HashSet<Cell>> c in cell.GetObservers())
{
count = count + c.Value.Count;
}
foreach (KeyValuePair<int, List<Cell>> k in cell.GetConnectedCells())
{
count = count + k.Value.Count;
}
if (count > bestCount)
{
bestCount = count;
}
}
value = bestCount;
return value;
}
public void GenerateStates(GameState gs, int depth, Boolean maxPlayer)
{
if(depth == 0 || gs.GetState().Equals(GameState.State.terminal))
{
return;
}
gs.FindChildrenStates(maxPlayer);
foreach(GameState child in gs.GetChildren())
{
if (maxPlayer)
{
GenerateStates(child, depth - 1, false);
}
else
GenerateStates(child, depth - 1, true);
}
}
