// calculates the score of the board from a player's prospective
int calc_score(char board[BOARD_SIZE][BOARD_SIZE], COLOR player){
int score = 0, opposites = 0;
for (int i = 0; i < BOARD_SIZE; i++)
for (int j = 0; j < BOARD_SIZE; j++){
if (is_opposite(player, board[i][j])) opposites++;
score += get_piece_score(board[i][j], player);
}
if (opposites == 0) return 100;
return score;
}
/* calculates the board's score.
* scoring_player = color of the minimax-maximizer player
* current_player = color of the player whose turn it is now.
*
* the function returns:
* WIN_SCORE if scoring_player wins this board
* LOSE_SCORE if scoring_player loses this board
* scoring_player's total pieces value minus other player's total pieces value otherwise
* ERROR_SCORE in case of an error
*/
int score(settings * set, int scoring_player, int current_player, int is_best){
int total_score;
cord piece;
moves possible_moves;
int no_more_moves = TRUE;
int no_scoring_king = TRUE;
int no_other_king = TRUE;
int num_of_moves;
int player_score = 0;
int other_player_score = 0;
int is_scoring_piece;
int is_scoring_checked = is_king_checked(current_player, set->board);
int is_other_checked = is_king_checked(other_player(current_player), set->board);
for (int i = 0; i < BOARD_SIZE; i++){
for (int j = 0; j < BOARD_SIZE; j++){
piece.x = i;
piece.y = j;
char cur_piece = board_piece(set->board, piece);
if (cur_piece == EMPTY)
continue;
int piece_color = which_color(cur_piece);
is_scoring_piece = (piece_color == scoring_player);
int piece_score = get_piece_score(cur_piece);
if (piece_score == KING_SCORE) {
no_scoring_king = (no_scoring_king && !is_scoring_piece);
no_other_king = (no_other_king && is_scoring_piece);
}
if (is_scoring_piece)
player_score += piece_score;
else //piece_color is other player's color
other_player_score += piece_score;
// we have to check that current_player has at least one piece that
// can move, otherwise current_player loses or it's a tie.
if (no_more_moves && (piece_color == current_player)) {
// check walking move for piece. checking move of distance 1 takes only O(1) time if
// player cannot move and O(n) if player can move (creating new board. occurs at most once)
// is enough for both king & man (if king cannot move 1 he cannot move 2)
possible_moves = get_simple_moves(set, piece);
num_of_moves = possible_moves.len;
free_list(&possible_moves, &free);
if (num_of_moves == -1) //there was an error, return an error score
return SCORE_ERROR;
// once one of the current_player can move, they do not lose,
// no need to preform this check again.
if (num_of_moves > 0) {
no_more_moves = FALSE;
}
}
}
}
// current_player cannot play.
if (no_more_moves) {
if (is_scoring_checked) // checkmate
total_score = (scoring_player == current_player) ? LOSE_SCORE : WIN_SCORE;
else // tie
total_score = is_best ? 0 : TIE_SCORE; // in best difficulty: 0, otherwise: better only than LOSE_SCORE
}
// scoring_player's king has ceased to be
else if (no_scoring_king)
total_score = LOSE_SCORE;
// other player's king is pushing up the daisies
else if (no_other_king)
total_score = WIN_SCORE;
//RELEVANT ONLY FOR best DIFFICULTY!
else if (is_best && is_scoring_checked) {
if (is_scoring_checked)
return LOSE_SCORE + 42;
else if (is_other_checked)
return WIN_SCORE - 42;
}
// both players' kings are alive and pining for the fjords
else
total_score = player_score - other_player_score;
return total_score;
}
