Question

To explain what I’m doing, I’m basically taking a string of X’s and O’s as an input String, converting it to an array, so XXXOXOXOO as the input would be the same array. Then I’m checking each possible scenario where one could win, coordinate wise, and if it matches it through if statements it returns the number corresponding to who won.

But it’s not quite working, haha. It seems to only output O as the winner, in clear cases where X should win.

Could anyone lend a hand? Much appreciated in advance, thanks.

import java.util.Scanner;
public class TicTacToe {
    public static void main(String[] args) {

        Scanner keyboard = new Scanner(System.in);

        System.out.println("Type in a board for analysis");
        String b = keyboard.nextLine();

        drawBoard(b);

        int result = decide(b);

        if (result == 1) {
            System.out.println("Win for X");
        }
        else if (result == 0) {
            System.out.println("Win for O");
        }
        else if (result == 3)  {
            System.out.println("Draw");
        }
        else {
            System.out.println("Game Unfinished");
        }
   }

    public static int decide(String scheme) {
        int decision = 0;

        String boardScheme[] = new String[9];

        for (int i = 0; i < 9; i++) {
            boardScheme[i] = scheme.substring(i,i+1);
        }

        if ((boardScheme[0] == boardScheme[1] && boardScheme[0] == boardScheme[2]) || (boardScheme[0] == boardScheme[3] && boardScheme[0] == boardScheme[6]) || (boardScheme[0] == boardScheme[4] && boardScheme[0] == boardScheme[8])) {
            if (boardScheme[0] == "X") {
                decision = 1;
            }
            else {
                decision = 0;
            }
        }
        else if (boardScheme[3] == boardScheme[4] && boardScheme[3] == boardScheme[5]) {
            if (boardScheme[3] == "X") {
                decision = 1;
            }
            else {
                decision = 0;
            }
        }
        else if (boardScheme[6] == boardScheme[7] && boardScheme[6] == boardScheme[8]) {
            if (boardScheme[6] == "X") {
                decision = 1;
            }
            else {
                decision = 0;
            }
        }
        else if (boardScheme[1] == boardScheme[4] && boardScheme[1] == boardScheme[7]) {
            if (boardScheme[1] == "X") {
                decision = 1;
            }
            else {
                decision = 0;
            }
        }
        else if ((boardScheme[2] == boardScheme[5] && boardScheme[2] == boardScheme[8]) || (boardScheme[2] == boardScheme[4] && boardScheme[2] == boardScheme[6])) {
            if (boardScheme[2] == "X") {
                decision = 1;
            }
            else {
                decision = 0;
            }
        }

        return decision;
    }

    public static void drawBoard(String scheme) {
        if (scheme.length() == 9) {
            String board[] = new String[9];

            for (int i = 0; i < 9; i++) {
                board[i] = scheme.substring(i,i+1);
            }

            System.out.println(board[0] + " | " + board[1] + " | " + board[2]);
            System.out.println(board[3] + " | " + board[4] + " | " + board[5]);
            System.out.println(board[6] + " | " + board[7] + " | " + board[8]);
        }
        else {
            System.out.println("Please input 9 characters, no more, no less.");
        }
    }
}

Answer 1

You are not covering all the possible cases. What would happen if you had missed a case? sorry, I went through them and indeed you do cover each case correctly. However, as noted by Hovercraft Full Of Eels in the comment to the question, you are comparing strings incorrectly. Still I would suggest the below.

You are setting decision = 0, so whenever a case occur which you are not covering, then you will end up returning 0. Which will output ‘O’ wins.

So, what you need to do is to figure out each possible case that can happen and then check for it. I would also suggest that you use codereview.stackexchange.com and ask for advice on how to restructure your code a bit, it will make it easier for you in the end.

For example what if you had a function horizontalWin(int column) and verticalWin(int row) and diagonalWin().

Good luck!