optimization Tic Tac Toe Game in C - c

Question

I'm beginner learner in C and one of the assignments I got was to write a Tic Tac Toe game. I have the game running but every time you place X on O position or vice versa it overwrites it. I would also appreciate comments on optimizing the code, because I'm a beginner and don't know a lot of concepts. Thank you! this is what I've got so far
#include<stdio.h>
void redrawBoard(char array[]);
void markBoard (int x, int o, char array[]);
int checkForWin(char array[]);
int checkForWin(char array[])
{
int a;
char x = 'X';
char o = 'O';
if (array[0] == x && array[4] == x && array[8] == x) // winning cases for x
return 1;
if (array[2] == x && array[4] == x && array[6] == x)
return 1;
if (array[0] == x && array[1] == x && array[2] == x)
return 1;
if (array[3] == x && array[4] == x && array[5] == x)
return 1;
if (array[6] == x && array[7] == x && array[8] == x)
return 1;
if (array[0] == x && array[3] == x && array[6] == x)
return 1;
if (array[1] == x && array[4] == x && array[7] == x)
return 1;
if (array[2] == x && array[5] == x && array[8] == x)
return 1;
if (array[1] == x && array[4] == x && array[6] == x && array[8] ==x) //checking for draw with x combinations 1st pattern
return 3;
if (array[0] == x && array[2] == x && array[4] == x && array[7] ==x)
return 3;
if (array[0] == x && array[4] == x && array[5] == x && array[6] ==x)
return 3;
if (array[2] == x && array[3] == x && array[4] == x && array[8] ==x)
return 3;
if (array[1] == x && array[4] == x && array[5] == x && array[6] ==x) //checking for draw with x combinations 2nd pattern
return 3;
if (array[0] == x && array[4] == x && array[5] == x && array[7] ==x)
return 3;
if (array[2] == x && array[3] == x && array[4] == x && array[7] ==x)
return 3;
if (array[1] == x && array[3] == x && array[4] == x && array[8] ==x)
return 3;
if (array[0] == o && array[4] == o && array[8] == o) //// winning cases for o
return 2;
if (array[2] == o && array[4] == o && array[6] == o)
return 2;
if (array[0] == o && array[1] == o && array[2] == o)
return 2;
if (array[3] == o && array[4] == o && array[5] == o)
return 2;
if (array[6] == o && array[7] == o && array[8] == o)
return 2;
if (array[0] == o && array[3] == o && array[6] == o)
return 2;
if (array[1] == o && array[4] == o && array[7] == o)
return 2;
if (array[2] == o && array[5] == o && array[8] == o)
return 2;
if (array[1] == o && array[4] == o && array[6] == o && array[8] == o) //checking for draw with o combinations 1st pattern
return 3;
if (array[0] == o && array[2] == o && array[4] == o && array[7] == o)
return 3;
if (array[0] == o && array[4] == o && array[5] == o && array[6] == o)
return 3;
if (array[2] == o && array[3] == o && array[4] == o && array[8] == o)
return 3;
if (array[1] == o && array[4] == o && array[5] == o && array[6] == o) //checking for draw with o combinations 2nd pattern
return 3;
if (array[0] == o && array[4] == o && array[5] == o && array[7] == o)
return 3;
if (array[2] == o && array[3] == o && array[4] == o && array[7] == o)
return 3;
if (array[1] == o && array[3] == o && array[4] == o && array[8] == o)
return 3;
else
return 0;
return(a);
}
void markBoard (int x, int o, char array[])
{
int i = 0;
char j = 'X';
char k = 'O';
while( x >= 1 && x <= 9)
{
array[x - 1] = j;
redrawBoard(array);
break;
}
while (o >= 1 && o <= 9)
{
array[o - 1] = k;
redrawBoard(array);
break;
}
}
void redrawBoard(char array[])
{
printf(" Player 1 is X; Player 2 is O;\n\n");
printf(" | | \n");
printf(" %c | %c | %c \n",array[0],array[1],array[2]);
printf(" ______|______|______ \n");
printf(" | | \n");
printf(" %c | %c | %c \n",array[3],array[4],array[5]);
printf(" ______|______|______ \n");
printf(" | | \n");
printf(" %c | %c | %c \n",array[6],array[7],array[8]);
printf(" | | \n");
}
int main()
{
int x;
int o;
char array[9] = {'1', '2','3','4','5','6','7','8','9'};
printf("tic tac toe game\n");
redrawBoard(array);
while (checkForWin(array) == 0)
{
printf("P1 start \n");
scanf("%d",&x);
markBoard(x,o,array);
printf("P2 go on\n");
scanf("%d", &o);
markBoard(x,o,array);
}
if (checkForWin(array) == 1)
printf("P1 won\n");
if (checkForWin(array) == 2)
printf("P2 won\n");
if (checkForWin(array) == 3)
printf("draw \n");
return 0;
}

Answer 1

The problem you mentioned is that you do not have a test when you already have a value in this cell.
About optimization:
Avoid a lot of if cases! Think about better check for checking who is winner.
For example, look at this check:
char winnerIs(char** Board, int i, int j) {
if (Board[i][j] == Board[i][(j+1)%3]
&& Board[i][j] == Board[i][(j+2)%3])
{
// got a column
return Board[i][j];
}
else if (Board[i][j] == Board[(i+1)%3][j] && Board[i][j] == Board[(i+2)%3][j])
{
// got a row
return Board[i][j];
}
else if (i == j && Board[i][j] == Board[(i+1)%3][(j+1)%3]
&& Board[i][j] == Board[(i+2)%3][(j+2)%3])
{
// got the forward diagonal
return Board[i][j];
}
else if (i+j == 2 && Board[i][j] == Board[(i+2)%3][(j+1)%3]
&& Board[i][j] == Board[(i+1)%3][(j+2)%3])
{
// got the reverse diagonal
return Board[i][j];
}
else {
// got nothing
return 0;
}
Avoid a lot of printing! Better use one structure for the game, for example a board - which is char board[][] or better char** Board if you want a dynamic game. And print the whole board once.
Instead of next code:
printf("P1 start \n");
scanf("%d",&x);
markBoard(x,o,array);
printf("P2 go on\n");
scanf("%d", &o);
markBoard(x,o,array);
Make something like this:
int player = 1;
char row, col;
player = (player % 2) ? 1 : 2;
scanf("%c %c", &row, &col);
markBoard(row, col, board);
Like that you don't need to duplicate a same code and it is automatic knows each turn, who's turn now.
Instead of next code:
if (checkForWin(array) == 1)
printf("P1 won\n");
if (checkForWin(array) == 2)
printf("P2 won\n");
if (checkForWin(array) == 3)
printf("draw \n");
Connect some conditions, like that:
if (checkForWin(array) == 1 || checkForWin(array) == 2) {
printf("Congratulations %c!\n", winner);
} else {
printf("Game ends in a draw.\n");
}
To make more "beauty" code, you can added a structs which will manage the whole game, for example:
typedef struct {
int size;
int **board; // the board
/* scores of all options */
int *rowScores;
int *colScores;
int topLeftBottomRightDiagonalScores;
int topRightBottomLeftDiagonalScores;
} Game;
typedef struct { // position on the board
int x;
int y;
} Position;
Your void markBoard (int x, int o, char array[]) function makes to much iterations to print the whole board. Better create the whole board once and after that run on the whole board.