tictactoe

commit ccc8a5e9822326c15197e154340e307e18c5a48e
parent 812bd5d20a182ea1b6e3cb5dbc8a06ce7b203106
Author: Wilson Gheen <wilson@wilsonrgheen.com>
Date:   Thu, 22 Dec 2022 12:55:11 -0600

End WIP. Finish (hopefully) unbeatable AI. No detected way for it to lose yet, but there is no random element to its moves

Diffstat:
M
tictactoe.h
 | 
26
+++++++++++++-------------

1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/tictactoe.h b/tictactoe.h
@@ -179,29 +179,29 @@ char get_winning_move_else_block_else_random(char *board, char player) {
 }
 static struct move minimax_best_move(char *board, char player, int *legal_moves, int lm_cnt) {
     char winning_moves[10] = "";
-    get_winner_or_winning_moves(board, winning_moves);
-    int his_wm_cnt = 0;
     int i;
+    char winner = get_winner_or_winning_moves(board, winning_moves);
+    int his_wm_cnt = 0;
+    int blocking_move = -1;
     for(i=0; i < 9; i++) {
         /* As good as won */
         if((winning_moves[i] & player) == player) {
             struct move m = {.move_ind = i, .winner = player};
             return m;
         }
-        /* `player` can't block both moves, so it's a loss */
-        if(winning_moves[i] == OPPONENT && ++his_wm_cnt > 1) {
-            struct move m = {.move_ind = i, .winner = OPPONENT};
-            return m;
+        if(winning_moves[i] == OPPONENT) {
+            his_wm_cnt++;
+            blocking_move = i;
         }
     }
-    i = 0;
-    for(int empties=0; i < 9; i++)
-        if(board[i] == ' ' && ++empties > 2) break;
-    if(i >= 9) {
+    if(lm_cnt <= 2) {
         /* If there's <= 2 moves remaining, and no opportunity
-         * to win next turn, it's a draw. (If the opponent has
-         * exactly one winning move, we will block it.) */
-        struct move m = {.move_ind = -1, .winner = 0};
+         * to win next turn, it's a draw. If the opponent has
+         * exactly one winning move, we will block it.
+         * If more than one, opponent wins. */
+        struct move m;
+        m.winner   = his_wm_cnt > 1 ? OPPONENT      : 0;
+        m.move_ind = his_wm_cnt > 0 ? blocking_move : legal_moves[0]; 
         return m;
     }