Tic Tac Toe - Quinn Batten

tictactoe.c

/*------------Libraries------------*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>


/*------------PRINT BOARD: prints the current board state------------*/
/*
Input: the current board state, represented by a char* of length 10 (9char+\0), where spaces that have been played
       in have an "X" or "O" (whichever player played there), and unplyed spaces have a lowercase letter between a
       and i, in increasing order from top left.
Output: Prints the board state, does not return any value.
*/
void printBoard(char *board)
{
    printf("\033[2J"); //clear screen
    printf("\n %c | %c | %c \n", board[0], board[1], board[2]);
    printf("-----------\n");
    printf(" %c | %c | %c \n", board[3], board[4], board[5]);
    printf("-----------\n");
    printf(" %c | %c | %c \n", board[6], board[7], board[8]);
}



/*------------GAME OVER: Prints congratulatory message------------*/
//Input: (int) If someone won, the int of the ASCII Char of the winner.
//Output: Prints the result of the game, then returns 1 (unless there's a problem).
int gameOver(int result)
{
    if ((int) result == 88 || (int) result == 79) //if X or O won
    {
        printf("\nGAME OVER!\nPlayer %c is the winner!!\n", (char) result);
        return 1;
    }
    else if (result == 1) //tie
    {
        printf("\nIt's a tie!!!\n");
        return 1;
    }
    else //Should never happen
    {
        printf("\nError in Game Over. Wrong result passed to fn.\n");
        return 0;
    }
}



/*------------CHANGE PLAYER: Changes the player whose turn it is, then prompts for the current player's move.------------*/
//Input: (char *player) the char representing the current player. Must be "X" or "O", aka (char) 88 or (char) 79.
//Output: (char) a char representing the NEW current player. Must be "X" or "O", aka (char) 88 or (char) 79.
char changePlayer(char player)
{
    if (player == 88) //X
    {
        player = 79;
    }
    else if (player == 79) //O
    {
        player = 88;
    }
    else //Should never happen
    {
        printf("ERROR IN MOVE: Wrong player passed");
    }
    return player;
}



/*------------PROMPT MOVE: Prompts for the current player's move.------------*/
/*
Input:
    1. (char *board) the current board state as a pointer to allocated memory (must be writable).
    2. (char *player) the char representing the current player. Must be "X" or "O", aka (char) 88 or (char) 79.
Output:
    (int) an integer between 0 and 8 (inclusive) represnting the space on the board that the current player
    wants to play in.
*/
int promptMove(char *board, char player)
{
    printf("Player %c, which space would you like to play?: ", player);
    int last = 41; //int value of ASCII character; used to check for double newlines & quits
    //loop to check validity of submission
    while (1 == 1)
    {
        int space; //int (0-8); the space on the board that the player has selected
        int input; //int value of ASCII character; the immediate, most recent typed value
        int answer = 0; //int value of ASCII character;where input goes if its not garbage.
        while ((input = getchar()) != EOF && input != '\n') //Toss newlines and EOF
//NOTE: Need to make this while loop more robust. I want it to only accept one char at a time & to toss ANSI escape codes, but haven't figured it out yet. Something with fgets, it sounds like.
        {
            if (answer == 0 && input >= 97 && input <= 105) //Check if it's an ASCII char btwn 'a' and 'i'
            {
                answer = input;
                space = answer - 97; //translate ASCII code to space in board array
                if (board[space] >= 97 && board[space] <= 105) //check if that space has been played
                {
                    return space;
                }
                else
                {
                    printBoard(board);
                    printf("\nThat space is taken already! Please try again:");
                }
            }
            else if (input == 113 || input == 81) //quit
            {
                last = input;
                printf("\nAre you sure you would like to quit? (y/n)\n");

            }
            else //they entered something weird
            {
                if ((last == 81 || last == 113) && (input == 89 || input == 121)) //if last key was qQ and this is yY, quit
                {
                    printf("\nQuitting game...\n");
                    exit(0);
                }
                printBoard(board);
                printf("Type in the letter of the space you want to play in.\nIt must be a lowercase letter between 'a' and 'i'.\n------\nPlayer %c, please try again:",
                      player);
            }
        }
    }
}



/*------------Checks whether a win has occurred------------*/
/*
Input: Current board state (see printBoard above, input is identical)
Output:
  - If someone won, the int of the char representing that player. Must be 88 (X) or 79 (O).
  - If the board is full but no win happened (aka a tie), return 1.
  - If no win yet, return 0.
*/
int checkGame(char *board)
{
    int tie = 0;
    for (int i = 0; i <= strlen(board); i ++)
    {
        //case: horizontal win
        if (i % 3 == 0 && board[i] == board[i + 1] && board[i] == board[i + 2])
        {
            return (int) board[i];
        }

        //case: vertical win
        else if (i <= 2 && board[i] == board[i + 3] && board[i] == board[i + 6])
        {
            return (int) board[i];
        }

        //case: diagonal win
        if (i == 0 || i == 2)
        {
            int add;
            if (i == 0)
            {
                add = 4;
            }
            else if (i == 2)
            {
                add = 2;
            }
            else //should never happen
            {
                printf("\nERROR in Board Check Function!!!\n");
                return 0;
            }

            if (board[i] == board[i + add] && board[i] == board[i + (2 * add)])
            {
                return (int) board[i];
            }
        }
        //counting filled spaces; if all spaces are filled, game's over (tie)
        if (board[i] == 88 || board[i] == 79)
        {
            tie = tie + 1;
        }
        if (tie > 8)
        {
            return 1;
        }
    }
    return 0;
}



int main(void)
{
    //Declare variables & allocate memory
    char playerChar = (char) 88; //current player
    char *boardState = "abcdefghi"; //initial board state
    int currMove = 0; //the space played in most recently (Current)
    int game = 0; //boolean for whether the game is still running
    char *oldBoard = malloc(10 * sizeof(char)); //old board state, just storage
    if (oldBoard == NULL)
    {
        return 1;
    }
    char *newBoard = malloc(10 * sizeof(char)); //new board state (Current)
    if (newBoard == NULL)
    {
        return 1;
    }

    //Assign correct initial values to old & new board states
    strncpy(oldBoard, boardState, 11);
    strncpy(newBoard, boardState, 11);

    //The big loop of play. Continues as play occurs, until game ends.
    while (game == 0)
    {
        printBoard(newBoard);
        playerChar = changePlayer(playerChar);
        currMove = promptMove(newBoard, playerChar);

        //Copy new board state into newBoard variable
        for (int i = 0, n = strlen(boardState); i < n; i++)
        {
            if (i == currMove)
            {
                newBoard[i] = playerChar;
            }
            else
            {
                newBoard[i] = oldBoard[i];
            }
        }
        strncpy(oldBoard, newBoard, 11);
        game = checkGame(newBoard);
    }
    printBoard(newBoard);
    return gameOver(game);
}