Question

−21 − (−7)2 − 6 − 9 + 4 × 7

Answer 1

#include <stdio.h>
#include <stdlib.h>

int b[3][3]; /* board. 0: blank; -1: computer; 1: human */

int check_winner()
{
int i;
for (i = 0; i < 3; i++) {
if (b[i][0] && b[i][1] == b[i][0] && b[i][2] == b[i][0])
return b[i][0];
if (b[0][i] && b[1][i] == b[0][i] && b[2][i] == b[0][i])
return b[0][i];
}
if (!b[1][1]) return 0;

if (b[1][1] == b[0][0] && b[2][2] == b[0][0]) return b[0][0];
if (b[1][1] == b[2][0] && b[0][2] == b[1][1]) return b[1][1];

return 0;
}

void showboard()
{
char *t = "X O";
int i, j;
for (i = 0; i < 3; i++, putchar('\n'))
for (j = 0; j < 3; j++)
printf("%c ", t[ b[i][j] + 1 ]);
printf("-----\n");
}

#define for_ij for (i = 0; i < 3; i++) for (j = 0; j < 3; j++)
int best_i, best_j;
int test_move(int val, int depth)
{
int i, j, score;
int best = -1, changed = 0;

if ((score = check_winner())) return (score == val) ? 1 : -1;

for_ij {
if (b[i][j]) continue;

changed = b[i][j] = val;
score = -test_move(-val, depth + 1);
b[i][j] = 0;

if (score <= best) continue;
if (!depth) {
best_i = i;
best_j = j;
}
best = score;
}

return changed ? best : 0;
}

char* game(int user)
{
int i, j, k, move, win = 0;
for_ij b[i][j] = 0;

printf("Board postions are numbered so:\n1 2 3\n4 5 6\n7 8 9\n");
printf("You have O, I have X.\n\n");
for (k = 0; k < 9; k++, user = !user) {
while(user) {
printf("your move: ");
if (!scanf("%d", &move)) {
scanf("%*s");
continue;
}
if (--move < 0 || move >= 9) continue;
if (b[i = move / 3][j = move % 3]) continue;

b[i][j] = 1;
break;
}
if (!user) {
if (!k) { /* randomize if computer opens, less boring */
best_i = rand() % 3;
best_j = rand() % 3;
} else
test_move(-1, 0);

b[best_i][best_j] = -1;
printf("My move: %d\n", best_i * 3 + best_j + 1);
}

showboard();
if ((win = check_winner()))
return win == 1 ? "You win.\n\n": "I win.\n\n";
}
return "A draw.\n\n";
}

int main(void)
{
int first = 0;
while (1) printf(game(first = !first));
return 0;
}

Answer 2

wrong answer

Answer 3

6

Answer 4

6

Answer 5

wrong

Answer 6

then what's the answer?