Question

I have a function for checking if an array has three of the same character for a tic-tac-toe array. Trouble is, I’m having an issue with the logic:

for (int i = 0; i < SIZE; i++){
    for (int j = 0; j < SIZE; j++){
        if (board[i][j] != '*'){
            if (i != j){
                if (board[i][i] == board[i][j]){
                    matches++;
                }
                else if (board[i][j] == board[j][i]){
                    matches++;
                }
                else if (board[i][j] == board[j][j]){
                    matches++;
                }
                else if (board[i][j] == board[j][i]){
                    matches++;
                }
                else {
                    matches = 0;
                }
            }
        }
    }
}

It seems that I can check for horizontally and vertically for matchings. But, I can’t quite figure out how to find the diagonal matchings. I thought this code would work and it so far has not.

Any suggestions about what is wrong?

Answer 1

Looks like homework, so I won’t give a code solution. But you can tell when you’re on a diagonal when either both indexes are equal (i == j), or when the indexes add up to one less than the dimension of the matrix (i + j == SIZE - 1.)

In the first case, you’re on the first diagonal (top-left to bottom-right.) In the second case, you’re on the second diagonal (top-right to bottom-left.)

This works for square matrices of any size.