tic_tac_terminal_toe.c

/* 
Tic Tac Toe

Write a program that lets two humans play a game of Tic Tac Toe in a terminal.
The program should let the players take turns to input their moves.
The program should report the outcome of the game.
*/

#include <stdio.h>


void main()
{
    int counter, player, go, grid_x, grid_y, line, winner = 0;
    char empty = ' ', x = 'X', o = 'O';
    char board[3][3] = {
        {empty, empty, empty},
        {empty, empty, empty},
        {empty, empty, empty},
    };

    /* Only 9 spaces at the board, so only 9 iterations */
    for (counter = 0; counter < 9 && winner == 0; counter++)
    {
        /* Print the board on each iteration */
        printf("\n\n\n");
        printf(" %c | %c | %c\n", board[0][0], board[0][1], board[0][2]);
        printf("---+---+---\n");
        printf(" %c | %c | %c\n", board[1][0], board[1][1], board[1][2]);
        printf("---+---+---\n");
        printf(" %c | %c | %c\n", board[2][0], board[2][1], board[2][2]);

        player = (counter % 2) + 1;
        /* Each coordinate pair on the grid will be assigned a number between 1 and 9 */
        do {
            printf("\nPlayer %d, please enter your go: ", player);
            scanf("%d", &go);
            grid_x = --go / 3;
            grid_y = go % 3;
        } while (
            go < 0 || 
            go > 9 || 
            board[grid_x][grid_y] == x ||
            board[grid_x][grid_y] == o
        );

        /* Sets the value in the game board */
        board[grid_x][grid_y] = (player == 1) ? x : o;

        for (line = 0; line <= 2 && winner == 0; line++)
        {
            /* Horizontal win */
            if (
                board[line][0] != empty &&
                board[line][0] == board[line][1] &&
                board[line][0] == board[line][2]
            ) 
            {
                winner = player;
            }

            /* Vertical win */
            if (
                board[0][line] != empty &&
                board[0][line] == board[1][line] &&
                board[0][line] == board[2][line]
            ) 
            {
                winner = player;
            }
        }
    
        /* Checking diagonal wins */
        if (
            board[0][0] != empty &&
            board[0][0] == board[1][1] &&
            board[0][0] == board[2][2]
        ) 
        {
            winner = player;
        }

        if (
            board[0][2] != empty &&
            board[0][2] == board[1][1] &&
            board[0][2] == board[2][0]
        ) 
        {
            winner = player;
        }
    }

    printf("\n\n\n");
    printf(" %c | %c | %c\n", board[0][0], board[0][1], board[0][2]);
    printf("---+---+---\n");
    printf(" %c | %c | %c\n", board[1][0], board[1][1], board[1][2]);
    printf("---+---+---\n");
    printf(" %c | %c | %c\n", board[2][0], board[2][1], board[2][2]);

    if (winner == 0)
        printf("\nHow boring, it is a draw.\n");
    else
        printf("\nCongrats, player %d. YOU ARE THE WINNER.\n", winner);
}