tictactoe

commit 6129d4dee09b1b24b41630d2068b56082010368c
parent ade02b2af7cc2149d34666c560ef839f9b804b09
Author: Wilson Gheen <wilson@wilsonrgheen.com>
Date:   Fri, 23 Dec 2022 13:09:23 -0600

Make minimax AI choose a random move if it's not a sure win or loss

Diffstat:
M
tictactoe.h
 | 
21
+++++++++++++--------
M
unit_test.c
 | 
2
+-

2 files changed, 14 insertions(+), 9 deletions(-)
diff --git a/tictactoe.h b/tictactoe.h
@@ -225,15 +225,20 @@ static struct move minimax_best_move(char *board, char player, int *legal_moves,
         }
     }
     /* No wins -- try for a draw */
-    while(lm_cnt-->0) {
-        if(moves[lm_cnt].winner == 0) {
-            struct move ret = moves[lm_cnt];
-            free(moves);
-            ret.move_ind = legal_moves[lm_cnt];
-            return ret;
-        }
+    int scratch_moves[9];
+    int sm_cnt = 0;
+    while(lm_cnt-->0)
+        if(moves[lm_cnt].winner == 0)
+            scratch_moves[sm_cnt++] = legal_moves[lm_cnt];
+    struct move ret;
+    if(sm_cnt) {
+        ret.winner = 0;
+        ret.move_ind = scratch_moves[get_rand(sm_cnt)];
+    }
+    else {
+        ret.winner = OPPONENT;
+        ret.move_ind = legal_moves[0]; //whatever
     }
-    struct move ret = moves[0]; //whatever
     free(moves);
     return ret;
 }
diff --git a/unit_test.c b/unit_test.c
@@ -68,7 +68,7 @@ int main() {
         printf("Result was: %s\n", actual_result);
         failures += print_test_results(i, !strcmp(actual_result, b->expected_result));
     }
-    failures += test_ai_against(get_move_minimax, 50, ++i, "itself", "a draw for all executions", false);
+    failures += test_ai_against(get_move_minimax, 500, ++i, "itself", "a draw for all executions", false);
     failures += test_ai_against(get_random_move, 500, ++i, "a random move generator", "the AI wins or draws for all executions", true);
     failures += test_ai_against(get_winning_move_else_random, 500, ++i, "a slightly dumber AI", "the AI wins or draws for all executions", true);
     failures += test_ai_against(get_winning_move_else_block_else_random, 500, ++i, "a slightly smarter, dumber AI", "the AI wins or draws for all executions", true);