tictactoe

commit be1fb705d3a882cb48e650355d4cba5352c45604
parent 7d8009aecfd298c86419f3e99249f9f08bc90e83
Author: Wilson Gheen <wilson@wilsonrgheen.com>
Date:   Sun, 18 Dec 2022 06:14:40 -0600

Fix up get_winner...() to detect moves that win for either player; add "AI" that blocks if it can't win this turn

Diffstat:
M
tictactoe.c
 | 
6
+++---
M
tictactoe.h
 | 
53
+++++++++++++++++++++++++++++++++++++++++++++--------
M
unit_test.c
 | 
1
+

3 files changed, 49 insertions(+), 11 deletions(-)
diff --git a/tictactoe.c b/tictactoe.c
@@ -6,20 +6,20 @@
 #include "../life/print_box.h"
 #include "tictactoe.h"
 
-#define SIDE_BY_SIDE 0
+#define SIDE_BY_SIDE 1
 
 static void print_board_offset(char *board, int offx, int offy, int clear) {
+#ifndef NO_PRINT_BOARD
     if(clear) tb_clear();
     print_box_offset(7, 7, offx, offy, 0);
     for(int i=0; i < 9; i++) {
         print_bw(((i%3) * 2) + 2 + offx, (i/3*2) + 2 + offy, board[i]);
     }
     tb_present();
+#endif
 }
 static void print_board(char *board) {
-#ifndef UNIT_TEST
     print_board_offset(board, 0, 0, 1);
-#endif
 }
 
 char play(char (*get_move)(char*, char)) {
diff --git a/tictactoe.h b/tictactoe.h
@@ -11,6 +11,7 @@
 #define O_WINS_ROW    " XXXOXOOO"
 
 #define scase(s1, s2)    if (!strcmp(s1, s2))
+/*#define NO_PRINT_BOARD*/
 
 /*typedef void (*board_fn)(char *, char);*/
 static char  the_desired_board[32];
@@ -26,6 +27,7 @@ static int get_rand(int max_excl) {
 char get_winner_or_winning_moves(char *b, char *winning_moves) {
     char center = b[4];
     _Bool add_to_wm = 0; 
+    /* Check status of squares on either side of center: row, column and diagonal */
     for(int i=-4; i < 0; i++) {
         int sq1 = 4+i;
         int sq3 = 4-i;
@@ -37,18 +39,21 @@ char get_winner_or_winning_moves(char *b, char *winning_moves) {
         }
         if(winning_moves == NULL) continue;
         if(add_to_wm) {
-            winning_moves[i] = b[sq1];
+            /* Normally means `w...[4] = b[s...]`, but allows us
+             * to detect later on if it is a winning move for both */
+            winning_moves[4] |= b[sq1];
             add_to_wm = 0;
         }
         else if(center == ' ') continue;
         else if((b[sq1] == center) ^ (b[sq3] == center)) {
             if(b[sq1] == ' ')
-                winning_moves[sq1] = center;
+                winning_moves[sq1] |= center;
             else if(b[sq3] == ' ')
-                winning_moves[sq3] = center;
+                winning_moves[sq3] |= center;
         }
     }
     for(int i=1; i <= 7; i+=2){
+        /* i&4 -> side column, else upper or lower row */
         int distance = ((i+1) & 4) ? 3 : 1;
         int sq1 = i - distance;
         int sq3 = i + distance;
@@ -60,15 +65,15 @@ char get_winner_or_winning_moves(char *b, char *winning_moves) {
         }
         if(winning_moves == NULL) continue;
         if(add_to_wm) {
-            winning_moves[i] = b[sq1];
+            winning_moves[i] |= b[sq1];
             add_to_wm = 0;
         }
         else if(b[i] == ' ') continue;
         else if((b[sq1] == b[i]) ^ (b[sq3] == b[i])) {
             if(b[sq1] == ' ')
-                winning_moves[sq1] = b[i];
+                winning_moves[sq1] |= b[i];
             else if(b[sq3] == ' ')
-                winning_moves[sq3] = b[i];
+                winning_moves[sq3] |= b[i];
         }
     }
     return 0;
@@ -101,6 +106,13 @@ char get_move_preset_board(char *board, char player) {
     }
     return 0;
 }
+char get_these_moves(char *board, char player) {
+    /* Automate any specific sequence of moves, for debugging */
+    static int moves[9] = {1, 2, 5, 6, 7,};
+    static int m = 0;
+    board[moves[m++]] = player;
+    return 0;
+}
 char get_move_from_human(char *board, char player) {
     int n;
     print_msg("%c's move? [1-9]: ", player);
@@ -118,18 +130,43 @@ char get_random_move(char *board, char player) {
     board[legal_moves[get_rand(lm_ind)]] = player;
     return get_winner_or_winning_moves(board, NULL);
 }
-char get_winning_move_else_random(char *board, char player) {
+static char try_get_winning_move(char *board, char player) {
     char winning_moves[9] = "";
     int my_winning_moves[5];
     int mwm_ind = 0;
     get_winner_or_winning_moves(board, winning_moves);
     for(int i=0; i < 9; i++)
-        if(winning_moves[i] == player)
+        if((winning_moves[i] & player) == player)
             my_winning_moves[mwm_ind++] = i;
     if(mwm_ind) {
         board[my_winning_moves[get_rand(mwm_ind)]] = player;
         return player;
     }
+    return 0;
+}
+char get_winning_move_else_random(char *board, char player) {
+    char winner = try_get_winning_move(board, player);
+    if(winner)
+        return winner;
+    else
+        return get_random_move(board, player);
+}
+char get_winning_move_else_block_else_random(char *board, char player) {
+    char winner = try_get_winning_move(board, player);
+    if(winner) return winner;
+    char winning_moves[9] = "";
+    int his_winning_moves[5];
+    int hwm_ind = 0;
+    char opponent = (player == 'O' ? 'X' : 'O');
+    get_winner_or_winning_moves(board, winning_moves);
+    for(int i=0; i < 9; i++)
+        if(winning_moves[i] == opponent)
+            his_winning_moves[hwm_ind++] = i;
+    if(hwm_ind) {
+        board[his_winning_moves[get_rand(hwm_ind)]] = player;
+        /*N.B. This will not be reached if the move is a winning move for both players */
+        return 0;
+    }
     else
         return get_random_move(board, player);
 }
diff --git a/unit_test.c b/unit_test.c
@@ -1,5 +1,6 @@
 #include <stdio.h>
 #define UNIT_TEST
+#define NO_PRINT_BOARD
 
 #include "tictactoe.c"