Tic-tac-toe

A game of tic-tac-toe is played on a 3×3  square grid. Each cell is either empty (denoted by '.') or occupied by one of the two players ('X' and 'O'). X goes first and then they take turns alternatively. If X is written three times in a straight line, then X wins and the game ends. The same goes for O. If there is no empty cell left, then the game ends as a draw.

You are given the description of a game of tic-tac-toe. You have to determine the state of the game.

The states of the game are as follows:

• If the game is invalid, that is, if there is no possibility of it happening, output "Wait, what?".
• If X has won, then print "X won." else if O has won print "O won.".
• If it is a draw, then print "It is a draw.".
• Otherwise, print whose turn it is, "X's turn." or "O's turn." accordingly.

Example:

Input: arr = {"O.X", ".OX", "..X"}
Output: X won.

Approach

C++

#include <bits/stdc++.h>
using namespace std;

char ticTacToe(map<int, char> &s)
{
    char winner = '.';
    if (s[1] == s[2] && s[1] == s[3] && s[1] != '.')
    {
        winner = s[1];
    }
    if (s[4] == s[5] && s[4] == s[6] && s[4] != '.')
    {
        if (winner == '.' || s[4] == winner)
        {
            winner = s[4];
        }
        else
            return 'E';
    }
    if (s[7] == s[8] && s[7] == s[9] && s[7] != '.')
    {
        if (winner == '.' || s[7] == winner)
        {
            winner = s[7];
        }
        else
            return 'E';
    }
    if (s[1] == s[4] && s[1] == s[7] && s[1] != '.')
    {
        if (winner == '.' || s[1] == winner)
        {
            winner = s[1];
        }
        else
            return 'E';
    }
    if (s[2] == s[5] && s[2] == s[8] && s[2] != '.')
    {
        if (winner == '.' || s[2] == winner)
        {
            winner = s[2];
        }
        else
            return 'E';
    }
    if (s[3] == s[6] && s[3] == s[9] && s[3] != '.')
    {
        if (winner == '.' || s[3] == winner)
        {
            winner = s[3];
        }
        else
            return 'E';
    }
    if (s[1] == s[5] && s[1] == s[9] && s[1] != '.')
    {
        if (winner == '.' || s[1] == winner)
        {
            winner = s[1];
        }
        else
            return 'E';
    }
    if (s[3] == s[5] && s[3] == s[7] && s[3] != '.')
    {
        if (winner == '.' || s[3] == winner)
        {
            winner = s[3];
        }
        else
            return 'E';
    }
    return winner;
}

int main()
{
    bool possible = true;
    map<int, char> spaces;
    int x = 0;
    int o = 0;
    vector<string> arr = {"O.X", ".OX", "..X"};
    for (int i = 0; i <= 2; i++)
    {
        string input = arr[i];
        if (input.size() != 3)
        {
            possible = false;
            break;
        }
        for (int j = 1; j <= 3; j++)
        {
            if (input[j - 1] == 'X')
            {
                spaces[i * 3 + j] = 'X';
                x++;
            }
            else if (input[j - 1] == 'O')
            {
                spaces[i * 3 + j] = 'O';
                o++;
            }
            else if (input[j - 1] == '.')
            {
                spaces[i * 3 + j] = '.';
            }
            else
            {
                cout << input[j] << "\n";
                possible = false;
                break;
            }
        }
    }
    if (!possible)
        cout << "Wait, what?";
    else if (o + 1 < x)
        cout << "Wait, what?";
    else if (o > x)
        cout << "Wait, what?";
    else
    {
        char winner = ticTacToe(spaces);
        if (winner == 'E')
            cout << "Wait, what?";
        else if (winner == 'X')
        {
            if (x == o)
                cout << "Wait, what?";
            else
                cout << "X won.";
        }
        else if (winner == 'O')
        {
            if (x != o)
                cout << "Wait, what?";
            else
                cout << "O won.";
        }
        else if (x + o == 9)
            cout << "It's a draw.";
        else if (x == o)
            cout << "X's turn.";
        else
            cout << "O's turn.";
    }

    return 0;
}