tictactoe

commit fe0f1f2cb5e0ae8e5656ce2e3136c392abcfed8b
parent b3d3893f89067fa04f2a6c7a35cd2a75fe63f566
Author: Wilson Gheen <wilson@wilsonrgheen.com>
Date:   Sat, 17 Dec 2022 09:28:24 -0600

Add function for "AI" that tries to win

Diffstat:
M
tictactoe.c
 | 
47
++++++-----------------------------------------
M
tictactoe.h
 | 
84
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------

2 files changed, 83 insertions(+), 48 deletions(-)
diff --git a/tictactoe.c b/tictactoe.c
@@ -22,56 +22,21 @@ static void print_board(char *board) {
 #endif
 }
 
-static void get_near_wins(char *b, char *winner) {
-    char winning_moves[9];
-    char center = b[4];
-    for(int i=-4; center != ' ' && i < 0; i++) {
-        int s2 = 4+i;
-        int s3 = 4-i;
-        if(b[s2] == center && b[s3] == center) {
-            *winner = center;
-            return;
-        }
-        if(b[s2] == center || b[s3] == center) {
-            if(b[s2] == ' ')
-                winning_moves[s2] = center;
-            else if(b[s3] == ' ')
-                winning_moves[s3] = center;
-        }
-    }
-    for(int i=1; i <= 7; i+=2){
-        if(b[i] == ' ') continue;
-        int distance = ((i+1) & 4) ? 3 : 1;
-        int s2 = i - distance;
-        int s3 = i + distance;
-        if(b[s2] == b[i] && b[s3] == b[i]) {
-            *winner = b[i];
-            return;
-        }
-        if(b[s2] == b[i] || b[s3] == b[i]) {
-            if(b[s2] == ' ')
-                winning_moves[s2] = b[i];
-            else if(b[s3] == ' ')
-                winning_moves[s3] = b[i];
-        }
-    }
-}
-
-char play(void (*get_move)(char*, char)) {
+char play(char (*get_move)(char*, char)) {
     struct tb_event ev;
     char board[9] = "         ";
     char winner = 0;
-    char last_played = 'O';
+    char player = 'O';
     if(!SIDE_BY_SIDE)
         print_board(board);
-    for(int turns=0; !winner && turns <= 9; turns++) {
-        get_move(board, (last_played = (last_played == 'O' ? 'X' : 'O')));
+    for(int turns=0; !winner && turns < 9; turns++) {
+        player = (player == 'O' ? 'X' : 'O');
+        winner = get_move(board, player);
         if(SIDE_BY_SIDE)
             print_board_offset(board, turns * 10, 0, 0);
         else
             print_board(board);
         tb_peek_event(&ev, 300);
-        get_near_wins(board, &winner);
     }
     return winner;
 }
@@ -80,7 +45,7 @@ char play(void (*get_move)(char*, char)) {
 int main(void) {
     struct tb_event ev;
     tb_init();
-    char winner = play(get_random_move);
+    char winner = play(get_winning_move_else_random);
     if(winner)
         print_msg("%c wins.", winner);
     else
diff --git a/tictactoe.h b/tictactoe.h
@@ -1,4 +1,6 @@
+#include <stdlib.h>
 #include <string.h>
+#include <time.h>
 
 #define SCRATCH_BOARD "XXOOOXXOX"
 #define X_WINS_COLUMN "XXOXOOXOX"
@@ -12,16 +14,49 @@
 
 /*typedef void (*board_fn)(char *, char);*/
 static char the_desired_board[32];
+static int  srand_seeded = 0;
 
-void get_move_preset_board(char *board, char player) {
-    char *desired_board = the_desired_board;
-    for(int i=0; i < 9; i++) {
-        if(desired_board[i] == player && board[i] == ' ') {
-            board[i] = player;
-            return;
+static int get_rand(int max_excl) {
+    if (!srand_seeded) {
+        srand(time(NULL));
+        srand_seeded = 1;
+    }
+    return rand() % max_excl;
+}
+char get_near_wins(char *b, char *winning_moves) {
+    char center = b[4];
+    for(int i=-4; center != ' ' && i < 0; i++) {
+        int s2 = 4+i;
+        int s3 = 4-i;
+        if(b[s2] == center && b[s3] == center)
+            return center;
+        if(winning_moves == NULL) continue;
+        if(b[s2] == center || b[s3] == center) {
+            if(b[s2] == ' ')
+                winning_moves[s2] = center;
+            else if(b[s3] == ' ')
+                winning_moves[s3] = center;
         }
     }
+    for(int i=1; i <= 7; i+=2){
+        if(b[i] == ' ') continue;
+        int distance = ((i+1) & 4) ? 3 : 1;
+        int s2 = i - distance;
+        int s3 = i + distance;
+        if(b[s2] == b[i] && b[s3] == b[i]) {
+            return b[i];
+        }
+        if(winning_moves == NULL) continue;
+        if(b[s2] == b[i] || b[s3] == b[i]) {
+            if(b[s2] == ' ')
+                winning_moves[s2] = b[i];
+            else if(b[s3] == ' ')
+                winning_moves[s3] = b[i];
+        }
+    }
+    return 0;
 }
+
 void set_board(char *board_name) {
     scase(board_name, "scratch_board")
         strcpy(the_desired_board, SCRATCH_BOARD);
@@ -39,10 +74,45 @@ void set_board(char *board_name) {
         strcpy(the_desired_board, O_WINS_ROW);
 }
 
-void get_move_from_human(char *board, char player) {
+char get_move_preset_board(char *board, char player) {
+    char *desired_board = the_desired_board;
+    for(int i=0; i < 9; i++) {
+        if(desired_board[i] == player && board[i] == ' ') {
+            board[i] = player;
+            return get_near_wins(board, NULL);
+        }
+    }
+    return 0;
+}
+char get_move_from_human(char *board, char player) {
     int n;
     print_msg("%c's move? [1-9]: ", player);
     tb_present();
     scanf("%d", &n);
     board[n-1] = player;
+    return get_near_wins(board, NULL);
+}
+char get_random_move(char *board, char player) {
+    int legal_moves[9];
+    int lm_ind = 0;
+    for(int i=0; i < 9; i++)
+        if(board[i] == ' ')
+            legal_moves[lm_ind++] = i;
+    board[legal_moves[get_rand(lm_ind)]] = player;
+    return get_near_wins(board, NULL);
+}
+char get_winning_move_else_random(char *board, char player) {
+    char winning_moves[9] = {0};
+    int my_winning_moves[5];
+    int mwm_ind = 0;
+    get_near_wins(board, winning_moves);
+    for(int i=0; i < 9; i++)
+        if(winning_moves[i] == player)
+            my_winning_moves[mwm_ind++] = i;
+    if(mwm_ind) {
+        board[my_winning_moves[get_rand(mwm_ind)]] = player;
+        return player;
+    }
+    else
+        return get_random_move(board, player);
 }