int abMax(int** board, int alpha, int beta, list<Move>& actions, Move move, int depth) {
switch(terminalState(board, move)) {
case Draw:
return 0;
break;
case Win:
return -INFINITE_SCORE;
break;
}
//Depth handling
if(depth==0)
return staticEvaluation(board);
if(depth != -1)
depth--;
list<Move>* children = legalMoves(board);
int v = -INFINITE_SCORE;
int w;
for(list<Move>::iterator it = children->begin(); it != children->end(); ++it) {
list<Move> &tmp = list<Move>();
int i = it->x;
int j = it->y;
doMove(board, *it, PLAYER_COLOR);
display(board);
w = abMin(board, alpha, beta, tmp, *it,depth);
undoMove(board, *it);
if(w > v) {
v = w;
actions = tmp;
actions.push_front(*it);
}
if(v >= beta)
return v;
alpha = max(alpha, v);
}
return v;
}
/**
* Alph-Beta Pruning
*@param depth how deep to search the tree
*@param alpha the minimax value for alpha
*@param beta the minimax value for beta
*@return x y coordinates for move
*/
int AlphaBetaAI::alpha_beta(AlphaBetaNode* node, int depth, int maxPlayer, int myScore, int otherScore, int pointsRemaining)
{
node->myScore = myScore;
node->otherScore = otherScore;
node->generateBoard(heapBoard);
if (depth <= 0 || pointsRemaining == 0) // or is a terminal node?
{
//printf("leaf node!\n");
int eval = evaluate(heapBoard, myScore, otherScore, maxPlayer);
return eval;
}
vector<int> legalMoves(node->getMoves());
//std::vector<int> moves;
//generateLegalMoves(_board, legalMoves); //vector of all possible legal moves to make
while (legalMoves.size()) //for each child node of max and min player
{
//printf("legal moves: %d\n", legalMoves.size());
int myPoints = myScore;
int otherPoints = otherScore;
int pointsLeft = pointsRemaining;
bool scored = makeNextMove(heapBoard, legalMoves[legalMoves.size()-1], maxPlayer, myPoints, otherPoints, pointsLeft);
AlphaBetaNode* kid = find_root(heapBoard, node, pointsLeft);
node->hasKid(kid);
kid->hasParent(node);
//printf("getting eval %d\n", kid);
float eval = alpha_beta(kid, 0, scored?maxPlayer:!maxPlayer, myPoints, otherPoints, pointsLeft);
/*if (scored) {
eval += eval+1;
}*/
//printf("got! eval %d\n", kid);
if (maxPlayer)
{
if (eval > node->alpha) {
node->alpha = eval;
}
//printf("%d %d\n", node->alpha, node->beta);
if (node->beta <= node->alpha) {
//printf("max-cut\n");
unmakeLastMove(heapBoard, legalMoves[legalMoves.size()-1]);
break; //beta cut-off
}
}
else
{
if (eval < node->beta) {
node->beta = eval;
}
//printf("\t\t\t%d %d\n", node->alpha, node->beta);
if (node->beta <= node->alpha) {
//printf("min-cut\n");
unmakeLastMove(heapBoard, legalMoves[legalMoves.size()-1]);
break; //alpha cut-off
}
}
//while (moves.size()) {
unmakeLastMove(heapBoard, legalMoves[legalMoves.size()-1]);
// moves.pop_back();
//}
legalMoves.pop_back();
break;
}//end while loop of all legalMoves
//printf("about to return thingy\n");
if (maxPlayer) {
return node->alpha;
}
return node->beta;
}
