Tic-tac-toe (25 points) In the Tic-Tac-Toe example done in class, we saw that there was a major problem with the function for entering players choice of box the player could enter anything, including numbers for boxes that had already been chosen. Of course, this is quite lame. Fix the function so that program checks to make sure that the choice entered is valid (an integer between 0 and 8) and that has not already been chosen. If a player tries to enter an invalid choice, the program a warning and give the user another chance to enter a proper value.

include

int checkForWinner(char*, int, char*);

void drawGrid(char a[]);

void takeTurn(char*, char*);

void swapPlayer(char*);

int main() {

char grid[9] = { '0', '1', '2', '3', '4', '5', '6', '7', '8' };

char currentPlayer = 'O';

int counter = 0, done = 0;

drawGrid(grid);

while (done == 0) {

takeTurn(grid, ¤tPlayer);

drawGrid(grid);

done = checkForWinner(grid, counter, ¤tPlayer);

swapPlayer(¤tPlayer);

counter++;

}

}

/** swapPlayer

Swaps current player from 'X' to 'O' and vice-versa **/

void swapPlayer(char *playerPtr) {

if (*playerPtr == 'X')

*playerPtr = 'O';

else

*playerPtr = 'X';

}

/** checkForWinner

Checks to see if there is a winner **/

int checkForWinner(char a[], int cnt, char* playerPtr) {

int i, gameOver = 0;

for (i = 0; i < 3; i++) {

if (a[3 * i] == a[3 * i + 1] && a[3 * i + 1] == a[3 * i + 2]) {

printf("We have a winner! It is %c. ", *playerPtr);

gameOver = 1;

}

if (a[i] == a[i + 3] && a[i + 3] == a[i + 6]) {

printf("Game over, man! %c dominates. ", *playerPtr);

gameOver = 1;

}

}

if (a[0] == a[4] && a[4] == a[8]) {

printf("%c wins on a diagonal move! ", *playerPtr);

gameOver = 1;

}

if (a[2] == a[4] && a[4] == a[6]) {

printf("That's it. %c has prevailed! ", *playerPtr);

gameOver = 1;

}

if (cnt == 8 && gameOver == 0) {

printf("Awww. It's a cat's game. ");

gameOver = 1;

}

return gameOver;

}

/** takeTurn

Tells the current player the available moves and enters the choice **/

void takeTurn(char a[], char *playerPtr) {

int available[9];

int i, j = 0, choice;

for (i = 0; i < 9; i++)

if ((a[i] != 'X') && (a[i] != 'O'))

available[j++] = i;

printf(" It is %c's turn. Choose your move (", *playerPtr);

for (i = 0; i < j; i++)

printf(" %d", available[i]);

printf(" ): ");

scanf("%d", &choice);

if (*playerPtr == 'X')

a[choice] = 'X';

else

a[choice] = 'O';

}

/** drawGrid

Draws the current state of the tic-tac-toe grid **/

void drawGrid(char a[]) {

printf(" ");

printf(" %c | %c | %c ", a[0], a[1], a[2]);

printf("---|---|--- ");

printf(" %c | %c | %c ", a[3], a[4], a[5]);

printf("---|---|--- ");

printf(" %c | %c | %c ", a[6], a[7], a[8]);

printf(" ");

}