// plays randomly
private Board Random_Bot(Board b)
{
while (true)
{
Random rnd = new Random();
if (b.AddPiece(2, rnd.Next(0, 7)))
{
break;
}
}
return(b);
}
// helper for minimax alg, recursively determines move strength
private int moveStrength(Board b, int move, int depth)
{
int currentPlayer = b.Turn;
Board copy = (Board)b.Copy();
if (copy.AddPiece(copy.Turn, move))
{
// if this move would spell an immediate win for either player
int winner = copy.Winner();
if (winner != 0)
{
// return the id of the current player * 10, with depth added
return((currentPlayer * 100) + depth);
//return (currentPlayer * 10);
}
}
// if the move is illegal, return -1
else
{
return(-1);
}
// base case: if depth has hit 0 (and no immediate win after this move established by previous step)
if (depth == 0)
{
return(0);
}
// otherwise, begin searching further through moves
else
{
bool tieAvailable = false;
int strongestMoveStrength = 0;
int bestBadMoveStrength = 0;
for (int c = 0; c < 7; c++)
{
int nextMoveStrength = moveStrength(copy, c, depth - 1);
// if the next move will ultimately result in a loss for currentPlayer, mark it as such
if ((nextMoveStrength / 100) == copy.Turn && nextMoveStrength > strongestMoveStrength)
{
strongestMoveStrength = nextMoveStrength;
}
// if at least one of the next moves will continue towards a potential victory for currentPlayer
else if (nextMoveStrength == 0)
{
tieAvailable = true;
}
else if (nextMoveStrength > bestBadMoveStrength)
{
bestBadMoveStrength = nextMoveStrength;
}
}
if (strongestMoveStrength > 0)
{
return(strongestMoveStrength);
}
else if (tieAvailable)
{
return(0);
}
else
{
return(bestBadMoveStrength);
}
}
}
// Same minimax algorithm but optimized with multithreading
private Board FasterMiniMax_Bot(Board b, int depth)
{
Array.Fill(strengths, -1);
Console.WriteLine("\nthinking...\n");
int bestWinningMove = -1;
int bestWinningMoveStrength = 0;
int bestAlternateMove = -1;
int bestAlternateMoveStrength = 1000;
depth += (7 - b.ValidMoveCount());
Console.WriteLine("Searching at depth " + depth + "...");
List <Thread> threads = new List <Thread>();
for (int i = 0; i < 7; i++)
{
Thread t = new Thread(new ParameterizedThreadStart(MeasureStrength));
MoveData data = new MoveData(b, i, depth);
t.Start(data);
threads.Add(t);
}
foreach (var thread in threads)
{
thread.Join();
}
for (int move = 0; move < 7; move++)
{
//int strength = moveStrength(b, move, depth);
if (strengths[move] != -1)
{
Console.WriteLine("Strength of move " + move + ": " + strengths[move]);
if ((strengths[move] / 100) == 2 && strengths[move] > bestWinningMoveStrength)
{
bestWinningMove = move;
bestWinningMoveStrength = strengths[move];
}
else if (strengths[move] == 0 || ((strengths[move] / 100) == 1 && strengths[move] < bestAlternateMoveStrength))
{
bestAlternateMove = move;
bestAlternateMoveStrength = strengths[move];
}
}
}
if (bestWinningMove != -1) // if there is a winning move to play, play the strongest one
{
//Console.WriteLine("\npursuing winning move: " + bestWinningMove);
b.AddPiece(2, bestWinningMove);
return(b);
}
else // if there is no winning move, play the optimal alternate one
{
//Console.WriteLine("\npursuing optimal alternate move: " + bestAlternateMove + " (strength " + bestAlternateMoveStrength + ")");
b.AddPiece(2, bestAlternateMove);
return(b);
}
}
// uses a more intuitive approach in combination with minimax algorithm to search for the strongest move
private Board BetterMiniMax_Bot(Board b)
{
Console.WriteLine("thinking...");
int bestWinningMove = -1;
int bestWinningMoveStrength = 0;
int bestAlternateMove = -1;
int bestAlternateMoveStrength = 1000;
List <int> tieMoves = new List <int> {
};
for (int move = 0; move < 7; move++)
{
// hardcoded depth of 6 move lookahead
int strength = moveStrength(b, move, 6);
if (strength != -1)
{
//Console.WriteLine("Strength of move " + move + ": " + strength);
if ((strength / 100) == 2 && strength > bestWinningMoveStrength)
{
bestWinningMove = move;
bestWinningMoveStrength = strength;
}
else if (strength == 0 || ((strength / 100) == 1 && strength < bestAlternateMoveStrength))
{
bestAlternateMove = move;
bestAlternateMoveStrength = strength;
if (strength == 0)
{
tieMoves.Add(move);
}
}
}
}
if (bestWinningMove != -1) // if there is a winning move to play, play the strongest one
{
Console.WriteLine("Pursuing CPU win");
b.AddPiece(2, bestWinningMove);
return(b);
}
else if (bestAlternateMoveStrength > 0) // if all moves are losing, play the optimal LEAST WEAK move
{
Console.WriteLine("Pursuing optimal losing move");
b.AddPiece(2, bestAlternateMove);
return(b);
}
////////////////////////////////////////////////////////////////////////////////
// ----- Otherwise, some moves suggest tie, so play more intuitively... ----- //
////////////////////////////////////////////////////////////////////////////////
Console.WriteLine("moves to consider:");
printIntList(tieMoves);
// if only one move is not losing, play it
if (tieMoves.Count == 1)
{
b.AddPiece(2, tieMoves[0]);
return(b);
}
// Otherwise, determine which of tying moves is optimal
// ideal columns to have pieces in, ordered from most ideal to least ideal
int[] idealColumns = { 3, 2, 4, 1, 5, 0, 6 };
for (int i = 0; i < idealColumns.Length; i++)
{
if (tieMoves.Contains(idealColumns[i]))
{
}
}
// placeholder, just play first available tie move
b.AddPiece(2, tieMoves[0]);
return(b);
}
// Continues to prompt users to play until a win or save occurs
// Returns a "w" for win or a "s" for save
public string PlayGame(Board b, int saveTurn)
{
bool win = false;
bool placed = false;
string x;
int VarCol;
int VarRow;
//Initialize the players
Player player = new Player()
{
piece = 'X',
turnNumber = 0
};
Player playerTwo = new Player()
{
piece = '0',
turnNumber = 1
};
int turn = saveTurn;
//Loops through a series of asking player one and two to input a location
//Assumes the location input is always formatted as 'row# col#' w/o error checking
do
{
//Player One plays
if (turn == 0)
{
b.DisplayBoard();
Console.WriteLine("Player One choose your location, row then column, or input save to save game");
Console.WriteLine("(for row 1 column 1 put: 1 1)");
x = SaveGame(Console.ReadLine(), b, player);
if (x == "save")
{
return("s");
}
// Try to get input
try
{
VarRow = Convert.ToInt32(x.Split(' ')[0]);
VarCol = Convert.ToInt32(x.Split(' ')[1]);
placed = b.AddPiece(VarRow, VarCol, player, b);
turn = 1;
}
//Catch any incorrect input and continue playing
catch (Exception)
{
Console.WriteLine("Invalid location: try again");
PlayGame(b, turn);
}
// If location was input correctly but is occupied
while (placed == false)
{
Console.WriteLine("Player One invalid location choose another location, row then column");
x = Console.ReadLine();
try
{
VarRow = Convert.ToInt32(x.Split(' ')[0]);
VarCol = Convert.ToInt32(x.Split(' ')[1]);
placed = b.AddPiece(VarRow, VarCol, player, b);
turn = 1;
}
catch (Exception)
{
Console.WriteLine("Invalid location: try again");
PlayGame(b, turn);
}
}
win = b.CheckWin(b, player);
// if Player One won
if (win == true)
{
b.DisplayBoard();
break;
}
}
//Player Two plays
if (turn == 1)
{
b.DisplayBoard();
Console.WriteLine("Player Two choose your location, row then column, or input save to save game");
x = SaveGame(Console.ReadLine(), b, playerTwo);
if (x == "save")
{
return("s");
}
// Try to get input
try
{
VarRow = Convert.ToInt32(x.Split(' ')[0]);
VarCol = Convert.ToInt32(x.Split(' ')[1]);
placed = b.AddPiece(VarRow, VarCol, playerTwo, b);
turn = 0;
}
//Catch any incorrect input and continue playing
catch (Exception)
{
Console.WriteLine("Invalid location: try again");
PlayGame(b, turn);
}
// If location was input correctly but is occupied
while (placed == false)
{
Console.WriteLine("Player Two invalid location choose another location");
x = Console.ReadLine();
try
{
VarRow = Convert.ToInt32(x.Split(' ')[0]);
VarCol = Convert.ToInt32(x.Split(' ')[1]);
placed = b.AddPiece(VarRow, VarCol, playerTwo, b);
turn = 0;
}
catch (Exception)
{
Console.WriteLine("Invalid location: try again");
PlayGame(b, turn);
}
}
win = b.CheckWin(b, playerTwo);
if (win == true)
{
b.DisplayBoard();
}
}
} while (win == false);
return("w");
}
