Occupied Position in Tic-Tac-Toe Game [C] - c

Question

One question about this code: if the choice the player picks is already taken, how do I make him/her choose again?
If I compile the code now, it will change the the position for the one the user chose, and this can't happen.
Obs: the "drawing" of the tic-tac-toe game should appear before this ("\nInform your choice (1-9): ")
This is the code:
char mat[9];
int main(void)
{
int i,jogada,casa,jogo=0;
for(i=0; i<= 9; i++)
mat[i] = ' ';
do{
printf("\n");
printf("\t|\t|\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n",mat[1],mat[2],mat[3]);
printf("--------|-------|-------\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n",mat[4],mat[5],mat[6]);
printf("--------|-------|-------\n");
printf("\t|\t|\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n\n",mat[7],mat[8],mat[9]);
printf("\nJOGADOR X ");
printf("\nInforme uma posicao livre (1-9): ");
scanf("%d",&casa);
}while((casa>=1)&&(casa<=9));
if((casa>=1)&&(casa<=9))
{
if(mat[casa] == 'X' || mat[casa] == 'O')
printf(" ");
else
mat[casa] = 'X';
}
printf("\n");
printf("\t|\t|\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n",mat[1],mat[2],mat[3]);
printf("--------|-------|-------\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n",mat[4],mat[5],mat[6]);
printf("--------|-------|-------\n");
printf("\t|\t|\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n\n",mat[7],mat[8],mat[9]);
if(mat[1] != ' ' && mat[1] == mat[2] && mat[2] == mat[3]) {
jogo++;
printf("X Ganhou!\n");
break; }
else if(mat[4] != ' ' && mat[4] == mat[5] && mat[5] == mat[6]) {
printf("X Ganhou!\n");
jogo++;
break; }
else if(mat[7] != ' ' && mat[7] == mat[8] && mat[8] == mat[9]) {
printf("X Ganhou!\n");
jogo++;
break; }
else if(mat[1] != ' ' && mat[1] == mat[4] && mat[4] == mat[7]) {
printf("X Ganhou!\n");
jogo++;
break;}
else if(mat[2] != ' ' && mat[2] == mat[5] && mat[5] == mat[8]) {
printf("X Ganhou!\n");
jogo++;
break; }
else if(mat[3] != ' ' && mat[3] == mat[6] && mat[6] == mat[9]) {
printf("X Ganhou!\n");
jogo++;
break; }
else if(mat[1] != ' ' && mat[1] == mat[5] && mat[5] == mat[9]){
printf("X Ganhou!\n");
jogo++;
break;}
else if(mat[7] != ' ' && mat[7] == mat[5] && mat[5] == mat[3]) {
printf("X Ganhou!\n");
jogo++;
break; }
else if((mat[1] != ' ') && (mat[2] != ' ') && (mat[3] != ' ') && (mat[4] != ' ') && (mat[5] != ' ') && (mat[6] != ' ') && (mat[7] != ' ') && (mat[8] != ' ') && (mat[9] = ' ')){
printf("Velha!\n");
jogo++;
break;
}
printf("\nJOGADOR O ");
printf("\nInforme uma posicao livre (1-9): ");
scanf("%d",&casa);
if((casa>=1)&&(casa<=9))
{
if(mat[casa] == 'X' || mat[casa] == 'O')
;
else
mat[casa] = 'O';
}
printf("\n");
printf("\t|\t|\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n",mat[1],mat[2],mat[3]);
printf("--------|-------|-------\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n",mat[4],mat[5],mat[6]);
printf("--------|-------|-------\n");
printf("\t|\t|\n");
printf("\t|\t|\n");
printf("%c\t|%c\t|%c\n\n",mat[7],mat[8],mat[9]);
if(mat[1] != ' ' && mat[1] == mat[2] && mat[2] == mat[3]) {
printf("O Ganhou!\n");
jogo++;
break; }
else if(mat[4] != ' ' && mat[4] == mat[5] && mat[5] == mat[6]) {
printf("O Ganhou!\n");
jogo++;
break; }
else if(mat[7] != ' ' && mat[7] == mat[8] && mat[8] == mat[9]) {
printf("O Ganhou!\n");
jogo++;
break; }
else if(mat[1] != ' ' && mat[1] == mat[4] && mat[4] == mat[7]) {
printf("O Ganhou!\n");
jogo++;
break; }
else if(mat[2] != ' ' && mat[2] == mat[5] && mat[5] == mat[8]) {
printf("O Ganhou!\n");
jogo++;
break;}
else if(mat[3] != ' ' && mat[3] == mat[6] && mat[6] == mat[9]) {
printf("O Ganhou!\n");
jogo++;
break; }
else if(mat[1] != ' ' && mat[1] == mat[5] && mat[5] == mat[9]){
printf("O Ganhou!\n");
jogo++;
break;}
else if(mat[7] != ' ' && mat[7] == mat[5] && mat[5] == mat[3]) {
printf("O Ganhou!\n");
jogo++;
break; }
else if((mat[1] != ' ') && (mat[2] != ' ') && (mat[3] != ' ') && (mat[4] != ' ') && (mat[5] != ' ') && (mat[6] != ' ') && (mat[7] != ' ') && (mat[8] != ' ') && (mat[9] = ' ')){
printf("Velha!\n");
jogo++;
break;
}
}
system("PAUSE");
return 0;
}

Answer 1

If the choice the player picks is already taken, how do I make him/her choose again?
Change your scanf() in 2 locations (X and O)
do {
printf("\nInforme uma posicao livre (1-9): ");
scanf("%d",&casa);
} while( (casa<1) || (casa>9) || (mat[casa] != ' ') );
You do have a bigger problem.
Change char mat[9] to char mat[10]. You are indexing your mat[] from 1 to 9 throughout your code. But char mat[9] only allows mat[0] to mat[8]. The quick fix is to make mat[] 1 char longer and not use mat[0]. Leave for(i=0; i<= 9; i++) as is.
OR -
A proper fix would be to keep char mat[9] and change all the many mat[i] references to mat[i-1]. e.g. mat[5] becomes mat[4]. Change to for(i=0; i < 9; i++).